Method and apparatus for commissioning power plants

ABSTRACT

An apparatus and method for commissioning steam turbine generator power plants to advance the cleanliness of the complete steam cycle by the conditioned discharge of steam to the plant surface condenser.

This application claims the priority date of Provisional ApplicationSer. No. 60/908,277, entitled METHOD AND APPARATUS FOR COMMISSIONINGPOWER PLANTS, filed on Mar. 27, 2007, which this applicationincorporates by reference in its entirety.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to the commissioning of new andrefurbished steam generation plant equipment and piping. Moreparticularly, the present invention relates to the cleaning andconditioning of metal surfaces in the steam and water circuitsassociated with steam turbine generators and similar equipment at thesame time that other essential commissioning activities are beingperformed.

Steam turbines convert thermal energy from pressurized steam intomechanical energy. This mechanical energy is commonly used to driveelectric generators or gas compressors. In combined cycle power plants,the exhaust heat of a gas turbine is used to generate steam that is thenused to power a steam turbine. In some types of gas turbine designs,some of the steam generated is also injected into the combustion path ofthe gas turbine to enhance the power output of the gas turbine.

Particulate debris may plug start-up screens installed at the inletcontrol valves of the turbines or clog narrow steam passages.Particulate debris may cause erosion or impact damage to both stationaryand rotating components of the steam turbines. Particulate debris mayalso plug or damage the internal surfaces of steam valves used tocontrol the flow of steam.

Silica oxides dissolved in steam are another critical contaminant thatmay be transported from the steam generation equipment and piping tosteam turbines. The solubility of silica oxides in the steam issignificantly increased with increasing temperatures. During the passageof steam through a steam turbine, the temperature of the steam isreduced. This will lead to a reduction of silica solubility and thedeposition of silica on the internal surfaces of the steam turbine.

Another critical type of contamination that may be transported from thesteam generation equipment and piping to the steam turbine are varioussalts. These salts include those that lead to high levels of cationconductivity in the steam condensate. Steam cation conductivity is theconductivity measured in steam condensate that has been passed through acation exchange resin. High cation conductivity results from anions. Thepresence of anions in the steam will lead to the potential of stresscracking of steam turbine components. Chlorides, organic anions andsulfates in the steam pose a particular danger for the onset of stresscracking.

Other presence of other salts, such as sodium, is also monitored in thesteam. The presence of sodium in the steam risks the deposition ofalkalis and/or other salts. Sodium chloride and sodium hydrogen sulfatealso constitute a risk of stress corrosion cracking of turbinecomponents.

In typical prior art methods for the commissioning of new andrefurbished steam turbine generator facilities, numerous methods havebeen employed to remove particulate contamination from the interiorsurfaces of the equipment and piping used to generate and transportsteam to steam and gas turbines.

One such method has been practiced for many decades and involves thepressurization of the steam generator with steam followed by the rapidrelease of the steam through a quick opening valve. This method istypically referred to as a “high pressure discontinuous steamblow”. Asecond method practiced for nearly the last twenty years involves thecontinuous discharge of low pressure/high velocity steam from the steamgenerators through the steam piping. This method is typically referredto as a “low pressure continuous steamblow”.

Still other methods of the art involve:

(a) the chemical cleaning of the steam generator and its associatedpiping before the steam generator is repeatedly pressurized with highpressure air that is released through a quick opening valve. [Thisprocess is typically referred to as an “air blow cleaning”];

(b) a high velocity water flush of the steam circuits, followed by achemical cleaning typically using EDTA followed by an extended steamblowthrough the steam system bypass valves to the condenser. This method istypically referred to as the “Siemens Augmented Bypass Operation”; and

(c) the chemical cleaning of the steam generator, followed by the highvelocity flushing of the steam path from the steam generator through thesuperheater, in addition to the high pressure water “hydro-milling” ofthe steam piping to the steam turbine. This method may also include asteamblow upon commissioning of the steam generator to the consenser toconfirm the absence of particulate contamination. This method isreferred to as the “LARCOM Process”.

In yet other variations of the above methods, a combination of chemicalcleaning of the steam generator and mechanical cleaning of the steampiping followed by a steamblow through the plant steam bypass system tothe condenser have been practiced. The mechanical cleaning of the steampiping may include the abrasive blasting of the pipe interior, hydromilling with high pressure water or other similar practices.

While all of the above prior art methods may be successful in theremoval of particulate contamination from the steam generator and pipedelivering steam to the steam turbine, the above prior art methods donot integrate the cleaning practices into other commissioning activitiesof the plant. They do not integrate the removal of particulatecontamination with the removal of other types of steam contaminationsuch as silica, cation conductivity and salts. Further the prior artcleaning methods typically limit the scope of the particulate debriscleaning effort to the steam generator, its associated piping and thesteam piping. Little if any effort is made to remove particulate andother contamination found in the condenser. In these prior art methods,the condenser may be flushed with water prior to initial operation ofthe steam generator. Contamination removed from the condenser may alsobe removed by use of condensate polishing beds following initial steamdischarge to the condenser.

Many of the prior art methods rely on the chemical cleaning of the steamgenerator and associated piping to reduce the potential for solidparticle contamination. Many of the chemical cleaning solutions containsodium, organic acids, organic corrosion inhibitors and other salts.Past experience has shown that it requires extensive post chemicalcleaning flushing to remove all residual salts that may “hide-out” insystems that have been chemically cleaned. These residues from thechemical cleaning may add to the level of sodium, cation conductivityand salts in the steam cycle of the plant. The chemical cleaningprocesses also generate large volumes of waste solution and waste flushwater.

Prior art methods make little effort to optimize conditions that willincrease the rate of silica, elements that contribute to cationconductivity and other salt contaminants. Removal of these contaminantsis typically left to the initial operation of the steam generator withsteam bypassed to the condenser. The operation of a plant in steambypass mode to the condenser is not optimized for the removal of silicaand other contaminating salts in the steam. Steam bypassed to thecondenser is cooled by addition of condensate to meet the designenthalpy limits of the condenser. Cooling of the bypass steam willresult in the precipitation of silica dissolved in the steam. In theprior art, the clean-up of the steam condensate to remove silica andother non-particulate contamination during turbine bypass operation isout of the scope of the existing steam system cleaning practices used toremove particulate contamination. In the prior art, before steam can bedischarged to the condenser through the bypass valves, the steam pathmust be cleaned to remove particulate contamination that may otherwisedamage those valves.

Many prior art methods are also highly dependent on vigilant maintenanceof the cleanliness of the systems cleaned prior to the initial operationof the steam generator. Corrosion following chemical cleaning,hydro-milling or other forms of mechanical cleaning may result in theformation of new particulate and salt contamination in the systemspreviously cleaned. Introduction of particulate contamination is alsopossible due to required mechanical work following many of the prior artmulti-stage cleaning methods. Many prior art systems require extensiveuse of welding to close access point required for the cleaning methods.Use of corrosion inhibitors or other agents to preserve the cleanedsurfaces may only exacerbate to amount of salts and organic compoundsthat will contaminate the steam during initial operation of the steamgenerator in bypass mode to the condenser.

The prior art practices of “discontinuous high pressure steamblow” andthe “low pressure continuous steamblow” exhaust all steam from the steamcycle during the cleaning process, these methods require large volumesof high quality water, may take weeks to complete, and can result inenvironmental issues such as noise, related to the discharge of largevolumes of steam. In addition, these methods do not generate conditionshighly favorable to the removal of silica, elements that result inelevated cation conductivity or other non-particulate steamcontamination.

These methods also do not involve the condenser and therefore do nothingto address contamination that might originate from the extensive amountof contaminated metal surface area in the condenser. These practicesalso require operation of the steam generator for an extended period oftime with little possibility for other normal commissioning activitiesto be performed. The fuel consumed during such steamblow operationsrepresents a significant expense. Extended operation of gas turbines ofcombined cycle power plants before tuning of the burners to minimizeemissions during prior art methods also results in significant exhaustemissions.

In addition to the above, the prior art practices make only limitedprovisions for the assured protection of the condenser during thedischarge of steam to the condenser. Specifically, none of the prior artpractices make adequate provisions to prevent the continued discharge ofsteam to the condenser should the condenser lose coolant flow or shouldattemperation water used to cool the steam being discharged to thecondenser be interrupted.

Prior art practices that rely on operation of the steam system in bypassmode through the bypass valve do not provide an assured means ofprotecting plant bypass valves from contamination or conditions that maycause the bypass valve to not close fully when plant conditions wouldrequire such closure to protect the condenser from damage. These sameprior art methods make no provision to insure that the conditionsgenerated by operation of the steam generation system in the bypass modewill optimize conditions for removal of either solid particle or othertypes of steam contamination due to the high pressure drop normallyassociated with typical bypass valves and the high back pressure oftypical steam distribution sparge tubes in the condensers. Although someprior art provides for the installation of sacrificial tubes in the toplayer of the condenser tube bank, none of the prior art cleaning methodsprovide for an assured means of shielding condenser tubes from highvelocity particles or moisture droplets discharged into the condenser athigh velocities.

Most prior art steam system cleaning methods do not provide for thecomprehensive treatment of the steam condensate generated in thecondenser during bypass mode operation. As a result, particulatecontamination found in this condensate will result in the plugging ofcondensate and boiler feedwater pump strainers. No particulatecontamination such as silica and dissolved salts are returned to thesteam generators. Use of ion exchange beds to remove salt ions isexpensive and is rarely applied.

Further, the prior art methods do not provide a means of cleaning thesteam exhausted from the steam generator and steam piping to removecontamination prior to the admission of the steam to the condenser.Contamination transported by the initial steam discharged to thecondenser will foul the condenser and may result in mechanical damage tothe condenser due to the high velocity impingement of particulatecontamination and entrained condensate droplets on the thin wallcondenser tubing. Although some prior art methods provide for theinstallation of a metal target plate into the bypass steam circuit tothe condenser to monitor the presence of particulate contamination, noneof the prior art methods make provision for the diversion ofcontaminated steam away from the condenser when particulatecontamination is indicated by such targets. The prior art also makes noprovision for diversion of steam with high concentrations of nonparticulate contamination until such time as the level of contaminationof the steam has been reduced to an acceptable level.

The prior art methods also make no special mechanical or chemicalprovisions during the operation of the steam generation equipment inbypass mode to create conditions that would enhance the removal of solidparticle and other forms of steam contamination from thesteam/condensate cycle.

In addition, prior art methods have not been practiced to generatephysical and chemical conditions in the steam path that will insure theformation of a passive coating on the metal surfaces consistent withthat formed by long term operation of the steam system at normaloperating conditions.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide animproved method for the cleaning of steam generation equipment andpiping that supply both steam and/or gas turbines with a process that isintegrated into the normal commissioning sequence of a new orrefurbished steam generation facility. In this manner, the normalcommissioning activities of the fuel supply, combustion and combustiongas exhaust systems as well as plant auxiliary systems may be tuned inparallel to the integrated cleaning activity. It is a further object ofthe present invention to reduce fuel and water consumption required forcleaning and commissioning. It is a further object of the invention tointegrate of the decontamination and other commissioning activities sothat, the time required to complete a project is significantly reduced.

One aspect of the present invention is to integrate the process ofremoving particulate contamination from the steam generator and steampiping circuits to the steam turbine with the process of removing othercontaminates such as silica, elements that contribute to high cationconductivity, sodium and other salts.

A further aspect of the present invention is inclusion of all elementsof the steam/condensate cycle in the commissioning/cleaning process toassure that all possible sources of contamination have been involved inthe cleaning process. The present invention provides for the dischargeof steam to the condenser for the bulk of the cleaning process. Thedischarge of clean steam to the condenser for the bulk of the steamsystem cleaning effort washes the extensive metal surface area of thecondenser at the same time that the remainder of the plant steam cyclesurfaces are being cleaned.

Another aspect of the present invention is generation of enhancedconditions during the initial operation of the steam generationequipment and piping that conveys steam to the steam turbine to provideassurance that the system will be rapidly cleared of particulatecontamination without the requirement for chemical cleaning of the steamgenerator or steam piping. This is accomplished by the operation of thesteam cycle at very high velocities and “cleaning force conditions”. Thetemporary piping and equipment provided for by this invention isdesigned to allow “base load” or 100% load operation of each individualsteam generator. Prior art steamblow techniques are typically practicedat loads of 25 to 35% of base load or less. As a result of the higherfiring rates provided for by the present invention, other commissioningactivities may be performed simultaneously with the effort to clean thesteam cycle of the particulate and non-particulate contamination.Operation at base load provides higher steam flow conditions and highersteam temperatures during the cleaning process. The high steam flowsrates improve both the rate and effectiveness of the process to removeparticulate contamination from the steam generator and steam piping. Thehigher steam temperatures benefit the removal of silica and othernon-particulate contamination from the steam generator and piping andpromote a more rapid formation of a stable passive film on the metalsurfaces of the steam path to the steam turbine.

Another aspect of the present invention is to avoid the sonicrestriction typically incurred by exhaust of the steam through thecommon blow out kits provided by the steam turbine manufacturers for thesteam stop valves at the inlet to the steam turbine at the end of thesteam flow path from the steam generator and steam piping. Experiencehas shown that these blow-out kits typically restrict the crosssectional area of the exhaust steam path creating a choke point in thesteam exhaust that will typically generate a sonic flow condition in theexhaust steam path. Such a sonic restriction will increase upstreampressures and result in lower steam velocities in the steam generatorsuperheater and steam piping. The lower velocities reduce theeffectiveness and rate of system cleaning. Experience has also shownthat many of the blow out kits for the turbine stop valves are notdesigned with materials capable of safely operating at the maximumdesign temperature of many of the steam systems being commissioned. Thetemperature limitation of a blow-out exhaust kit for a steam turbinestop valve would prevent base load operation of the unit at fulloperating temperatures. The higher temperatures increase both theeffectiveness and rate of removal of both the particulate and nonparticulate contamination from the steam path to the steam turbine.

To prevent the above limitations, the present invention provides for theinstallation of a larger exhaust nozzle on the steam piping immediatelyprior to the steam turbine inlet valve. This connection is designed tolimit the restriction of the exhaust steam flow cross section to allowbase load operation of the steam generator while minimizing thegeneration of backpressure from a sonic condition in the temporary steamexhaust piping.

Another aspect of the present invention is to install temporary pipingof a material class suitable for steam temperatures up to the maximumdesign conditions of the steam at base load operation. The ability tosafely operate with steam flows and temperatures up to the base loadconditions improves the effectiveness and speed of removal of bothparticulate and non particulate contamination but also facilitate thesimultaneous ability to tune steam generator burners and other equipmentnecessary for normal plant commissioning.

In a variation of the present invention, restriction of the lowtemperature rating and limited cross sectional flow area of a steamturbine manufacturer's blow kit is mitigated by the addition of atemporary means of adding condensate or boiler feedwater to the plantsteam piping upstream of the blow kit. By addition of water to the hightemperature steam upstream of the blow kit, the temperature of the steamis lowered within the design temperature range of the blow kit. At thehigh steam flow conditions generated by base load operation of the steamgenerators, the pressure of the steam passing through the blow kit iskept sufficiently high as to limit the adverse potential of a sonicdischarge through the constricted cross sectional flow area of the blowkit.

Due to the novel steam conditioning equipment employed by the presentinvention, chemically treated condensate can be safely added to the highvelocity steam to form an annular mist in the circuits of the steamcycle as the interior surfaces of the steam generation equipment andpiping are being cleaned by the high velocity steam as the steam isbeing exhausted to the condenser. When condensate is injected into thesuperheated, high velocity steam, the water droplets will evaporatereducing the temperature of the steam. The rate of droplet evaporationis limited by the decreasing surface area of the droplets available toallow heat to be transferred from the superheated steam into theremaining condensate droplet. As a result, the droplets will persist forsome period of time in a two phase flow condition of high velocity steamand entrained droplets. Scientific literature describes such a two phaseflow regime as an annular mist. The annular mist condition will persistfor some distance downstream of the condensate injection point due tothe time required to effect the complete evaporation of the liquiddroplets into the steam. Staging the injection of the condensate atvarious points along the steam path will assure all interior surfaces ofthe pipe are effectively washed by the entrained water droplets. Inprior art practice, addition of condensate droplets to steam beingdischarged to a condenser would not be practiced due to the risk ofcarryover of the high velocity droplets into the condenser with thepotential that such droplets, and the solid particle contamination theydisengage from the steam path interior surfaces could result in erosivedamage to the thin walled condenser tubes.

Entrainment of water droplets in the high velocity steam generates amore erosive condition as the high velocity steam flows through thesteam path from the steam generator to the steam turbine. Impact ofthese high velocity water droplets on the interior metal surfaces of thesteam path will more rapidly and effectively dislodge adhered solidparticle contamination from the steam path surfaces. The present patentalso makes provision for the removal of entrained water droplets in thesteam before it is discharged to the condenser. In this manner,contamination of the condenser by the dirty steam being exhausted fromthe steam generator and piping is avoided. By removal of the entrainedsolid particle contamination and entrained water droplets from the highvelocity steam entering the condenser, the present invention assuresthat the thin walled tubes in the condenser will not be eroded byimpingement of those surfaces by high velocity particles or waterdroplets.

In addition to the enhanced cleaning effect of entrained water dropletsexhibit to adhered solid particle contamination, the liquid waterdroplets impacting the interior surfaces of the steam path from thesteam generator to the steam turbine also enhance the removal of silicaand other non-particulate contaminants from the steam path surfaces. Dueto the fact that the present invention conditions the steam exhausted tothe condenser and does not require the steam to be lost to theatmosphere, volatile chemical agents may be added to the steam and theinjected condensate in sufficient concentrations to create a chemicalenvironment more conducive to the removal of silica and othernon-particulate contamination found on those surfaces.

The addition of ammonium hydroxide in sufficient concentration toincrease the pH of the steam above 10.0 and preferably above 10.5significantly enhances both the rate and effectiveness of silicasolubility into the cleaning flow of steam. The high pH and the presenceof the liquid water droplets further reduces the potential for thesilica and other salts to redeposit onto the steam path surfaces or ontothe surfaces of the condenser tubes. Use of high pH condensate to washthe steam in the steam conditioning equipment prior to the condenseralso helps to reduce the amount of non-particulate contamination that isdischarged to the condenser.

Due to the much more aggressive flushing conditions generated by thesteam and the two phase steam/condensate flows at the higher steamproduction rates facilitated by the current invention, the requirementfor chemical cleaning of the steam superheater surfaces and steam pipingis eliminated. As a result, potential sources of residualnon-particulate steam contamination from the chemical cleaning areminimized in addition to eliminating the cost and disruption of thechemical cleaning activity to the commissioning schedule, the cost andenvironmental impact of the chemical cleaning waste disposal, therequirement for extensive flushing following the chemical cleaning andthe need to vigilantly maintain chemically cleaned systems to preventcorrosion and recontamination between the time the chemical cleaning hasbeen performed and the steam generator and steam piping are put intoservice.

Another aspect of the present invention is to limit the amount of highquality water that will be consumed during the cleaning andcommissioning efforts. The elimination of the chemical cleaning and postchemical cleaning flushes reduces the amount of water consumed by thosepractices. In addition, the present invention provides for the recoveryof a vast majority of the steam used to purge the steam path ofcontaminants by means of washing the contaminated exhaust steam prior toits admission to the condenser and by treatment of the condensatereturned from the condenser. Reduction of water consumption during thecommissioning phase of a new or refurbished steam turbine facilityreduces cost and facilitates the plant commissioning schedule insituations where the supply of high quality make-up water is limited.

A further aspect of the present invention is to provide enhanceprotection of the condenser during the initial discharge of steam to thecondenser. The present invention provides for the use of a soft metaltarget inserted into the exhaust flow from the steam conditioningequipment used to treat the exhaust steam prior to discharge of thesteam to the condenser to assure that steam flow to the condenser isproperly conditioned and free of all erosive solid particles andentrained water droplets. In addition, the present invention providesfor a novel means of monitoring both the influent and effluent of thesteam conditioning system to assure that both particulate andnon-particulate contamination is removed from the exhaust steam prior tothe admission of the steam to the condenser.

During the initial discharge of steam from the plant steam circuits, thepresent invention provides for a diversion means to discharge highlycontaminated steam to the atmosphere instead of the condenser. Polishedmetal targets are inserted into the inlet and outlet of the exhauststeam conditioning equipment disclosed in this invention. A comparisonof these targets provides assurance that all harmful particulatecontamination is removed from the exhaust steam prior to the dischargeof any exhaust steam to the condenser. In addition, steam condensatesamples are taken from both the inlet and outlet of the exhaust steamconditioning equipment. Analysis of this condensate allows theconcentration of silica and other non particulate contaminants to bemonitored while steam is initially diverted from the condenser to theatmosphere. Only after comparison of the polished metal targets at theinlet and outlet of the exhaust steam conditioning equipment and thechemical analysis of the steam condensate from both the inlet and outletof the exhaust steam conditioning equipment demonstrates that the steamcleanliness is sufficient to allow safe discharge of exhaust steam tothe condenser is the steam diverted away from the atmospheric dischargeand allowed to enter the condenser.

Another aspect of the present invention is the modification of theexisting bypass steam system to allow steam discharge to the condenserunder conditions more favorable to the overall cleaning process as wellas to reduce the energy of the steam discharged to the condenser. Thepresent invention provides for the installation of a modified steamdiffuser in the condenser to reduce the backpressure of the steamentering the condenser. By substantially reducing the backpressure onthe steam entering the condenser, higher velocities are achieved in theplant piping and steam generation equipment. Reducing the backpressureof the steam entering the condenser also lowers the design pressure ofthe temporary piping and steam conditioning equipment.

In addition the present invention also provides for the installation ofa porous impingement shield between the diffuser and the top surface ofthe thin walled condenser tubes. The impingement shield provides atortuous path for the steam and any entrained particles and dropletsthat may still enter the condenser despite the effect of the steamconditioning equipment provided for by the present invention. Inaddition to acting as an impingement surface to spoil the velocity ofany solid particles or water droplets that may be entrained in the steamentering the condenser, this shield also acts to more uniformlydistribute the steam within the condenser. The combined effect of thesemeasures is to reduce the potential for solid particle and high velocitywater droplet impingement on the thin walled condenser tubes, and thepotential of damage to condenser tubes as the result of localizedheating or excessive vibration of condenser tubes due to the poordistribution of high energy steam into the condenser.

Another aspect of the present invention provides specially designedtemporary equipment to assure that steam flow to the condenser may berapidly terminated when conditions occur that may expose the condenserto potential damage. Should cooling water flow to the condenser be lost,serious damage to the condenser tubes and tubesheets will occur in ashort period of time due to the overheating of the condenser tubes. Suchan occurrence may also result in the failure of the condenser ruptureplate due to an excessive pressure in the steam chest of the condenser.An over-temperature condition may also occur with the loss of the quenchand wash water flow into the exhaust steam. In such an event thetemperature of the steam will quickly rise above the design limits ofthe condenser.

The present invention provides for a set of rapidly actuated valves thatwill divert exhaust steam from the path to the condenser andsimultaneously open the discharge of the steam to an atmospheric vent.The actuators of these valves are provided a secure source of power toassure operation of the valves even in the event of a plant powerfailure. The combined effect of these valves also provides a means ofprotecting against a sudden increase in the operating pressure above thedesign pressure of the temporary piping and the steam conditioningequipment. The present invention also provides for the installation of aredundant overpressure protection means that will automaticallydischarge steam to the atmosphere should the operating pressure of thetemporary piping and steam conditioning equipment exceed the designedoperating pressure of these systems.

Another objective of the present invention is to provision of a methodand means to remove particulate and other non-particulate contaminatesfrom the steam cycle in a highly efficient manner. Experience has shownthat the initial steam exhausted from new or refurbished steamgeneration equipment and piping will contain very high concentrations ofboth solid particle and non-particulate contamination. In the presentinvention, this initial steam exhaust is passed through the steamconditioning equipment where the steam is washed with condensate andthen the dirty liquid condensate is separated from the treated exhauststeam. The equipment provided for by this invention allows this washedsteam to be discharged to the atmosphere as it may still contain somecontamination. During this initial phase of the cleaning cycle, thesteam wash effluent from the separator section of the steam conditioningequipment is channeled to waste. This wash water effluent is tested todetermine the concentrations of both suspended and dissolvedcontamination. A soft metal target is also inserted into the steamexhaust from the steam conditioning equipment. This initial orientationof the system is continued until the level of contamination in the steamwash water effluent and the appearance of the soft metal target in thesteam effluent from the conditioning equipment indicate that the exhauststeam cleanliness is adequate for discharge to the condenser. Inaddition, the present invention provides for the continued washing ofthe exhaust steam through the duration of the cleaning process and thecontinued monitoring of the cleanliness of the steam entering andexiting the steam conditioning equipment.

The present invention also provides for the interception of all of thecondensate from the condenser hot well before it is returned to thesteam generation equipment. Experience has shown that the initialcondensate from the condenser will have high levels of particulate andnon-particulate contamination. Initially the intercepted condensate issegregated and discharged to waste. During this initial period, thepresent invention provides for the temporary supply of clean condensateto the steam generation equipment. Once testing of the condensatereturned from the condenser indicates that the heaviest concentrationsof contamination are beginning to wane, the present invention providesfor the treatment of the condensate collected in the condenser to makethe condensate suitable for return to the steam generation equipment.The treatment of the condensate includes passage of the condensatethrough a set of filters with a designed flow capacity sufficient.

The considerable amount of metal surface in the condenser provides asignificant source of both particulate and non-particulate contaminationto the steam cycle. Prior art practices have not provided for thetreatment of the initial full flow of condensate to adequately removethis contamination from the condensate returned from the condenser. Thesuction strainers on the plant condensate pumps typically are not fineenough to remove a significant amount of particulate contamination fromthe condensate returned from the condenser. The design of the normalplant condensate suction strainers is also inadequate to have thecapacity to remove a significant quantity of contamination before thesuction strainer is plugged and the condensate pump must be removed fromservice. In many cases, it is common for the plugging of condensate pumpstrainers to result in an unplanned shut-down of the plant resulting ina disruption and delay of the plant commissioning effort. Operation ofthe plant condensate pumps without adequate protection from thedetrimental ingestion of particulate contamination by the condensatepumps risks damage to these pumps as well as the plugging or damage toflow control valves in the condensate and boiler feedwater piping. Thepassage of excessive quantities of particulate contamination from thecondenser into the condensate and feedwater piping also risks thepotential for the plugging of the suction strainers of the boilerfeedwater pumps. Again it is a common experience that particulatecontamination collected in the boiler feedwater pump suction strainerswill cause the boiler feedwater pumps to cease operation with the resultthat an unplanned outage of the plant during commissioning will occur.

In addition to the use of fine filters to remove solid particlecontamination, the present invention provides for temporary pumpsspecifically design to pull suction from the condenser hotwell anddischarge the dirty condensate to the filters. These pumps are designedto draw suction into the pump to overcome the low net positive suctionhead generated by the vacuum of the condenser. These pumps are alsodesigned with adequate clearance to allow passage of particulatecontamination without damage to the temporary pump. The temporarycondensate pumps may also be equipped with multiple suction strainers toallow the continuous operation of the temporary pump even though solidparticle debris has collected in one of the suction strainers.

In addition to the filters, the condensate may also be treated bypassage through ion exchange resin beds or other types of watertreatment equipment to remove dissolved salts and silica from thecondensate.

Another aspect of this invention is provision of a means for thetreatment of the effluent condensate from the steam conditioningequipment. Experience has shown that after some period of time thecleanliness of the steam exhausting from the steam generation and steampipe path to the steam turbine will substantially improve. Although thecleanliness of this steam is still insufficient to warrant terminationof the cleaning effort, the steam conditioning wash condensate issufficiently clean to allow this effluent to be treated to make itsuitable for return to the steam generation equipment. By providing forthe treatment of the steam conditioning equipment wash effluent, thepresent invention further reduces the amount of water consumed by thecleaning program.

Another aspect of the present invention is protection of the steamturbine by the installation of a supplemental means of cooling theexhaust hood of the steam turbine that is common to the inlet to thecondenser. When steam is exhausted to a condenser that is incommunication with the steam turbine, it is normal practice for thesteam turbine rotor to be rotated to insure that the rotor is uniformlyheated by any steam with which it may come in contact. Injection ofsupplemental condensate spray into the steam turbine exhaust hood beyondthat normally provided by the plant design insures that the prolongeddischarge of steam to the condenser will not result in the differentialheating of the steam turbine rotor and casing. Localized heating of therotor at a rate or to an extent that results in the differentialexpansion of the rotor compared to the casing may result in aninterference between these two steam turbine components. Such aninterference or rub may prevent the continued rotation of the steamturbine rotor. In such an event, continued discharge of steam to thecondenser would need to be terminated to avoid the potential for theuneven heating of the steam turbine rotor. An uneven heating of thesteam turbine rotor could result in the bending of the steam turbinerotor shaft. Normal plant designs provide for the injection ofcondensate into the exhaust hood of the steam turbine. In the presentinvention, the plant hood spray system may be supplemented by anadditional system of condensate sprays to assure the continued additionof large volumes of exhaust steam into the condenser without thedifferential heating of the steam turbine components.

Another aspect of the present invention is generation of conditionsduring the combined cleaning/commissioning of the steam generator andsteam path so as to generated a highly passive condition on the metalsurfaces of the steam path consistent to that generated during normaloperation of the steam systems. The present invention accomplishes thisby operation of the steam path at the elevated temperatures achieved atthe higher load rate as well as by the addition of volatile chemicalagents that will effectively generate such a passive surface rapidlyduring the combined cleaning and commissioning activity described bythis present invention.

Another aspect of the present invention is the provision for temporarycondensate storage, pumps and piping to provide a secure source ofcondensate to the plant and temporary equipment even though the normalplant system may no longer be available for service. It is not uncommonduring the commissioning of a new or substantially refurbished plant forthe power supply system of the plant to suffer an unexpected outage. Toprevent damage to plant equipment due to the sudden loss of condensaterequired to control the steam temperature, the present inventionprovides for sufficient condensate storage, pump capacity and piping toprovide such condensate flow as necessary to support temperature controlof the steam up to the base load condition of the plant. To insure thatpower to the temporary pumps is not lost in the event of a temporaryplant power failure, the temporary pumps may be driven by a dieselengine or by electric motors powered by temporary diesel generators.

Another aspect of the present invention is provision of a separate meansof overpressure protection on the steam conditioning equipment and thetemporary piping to provide assurance that an incorrect operation of thetemporary valves used to direct the steam during the cleaning andcommissioning effort cannot result in the a condition wherein thedesigned operating pressure of the temporary steam conditioningequipment and temporary piping is exceeded.

The above and other objects and aspects of the present invention willbecome apparent from the drawings, the descriptions given herein, andthe appended claims.

In one embodiment, the present invention provides for the washing of theinterior surfaces of the steam path at steam production rates that allowinitial tuning of the “Dry Low NOx” (DLN) burners of a gas turbineand/or the performance of a required extended period of base loadoperation of the gas turbine to allow removal of the start-up strainersfrom the gas supply piping to the gas turbine burners.

Due to the high rates of steam production during the extended timerequired to complete these normal commissioning activities of a gasturbine combined cycle power plant, the prior art methods that exhauststeam to the atmosphere are not practical as a result of the largeamounts of high quality make-up water required. In the prior art methodsthat call for the discharge of exhaust steam to the condenser, the useof the normal steam bypass system to divert the steam prior to the steamturbine entry limits the cleaning conditions due to the higherbackpressure of the normal bypass systems. These latter prior artmethods also require extensive chemical and mechanical cleaning methodsprior to the use of the plant bypass systems. In addition, passage ofsteam through the normal plant bypass systems risks potential damage tothe bypass valves and to the thin walled condenser tubing.

Past experience has shown that the passage of contaminated steam throughthe bypass valves risks damage to these valves to the extent that theymay be unable to close completely in the event that plant conditionsrequire the termination of steam flow to the condenser. In such cases,the condenser may incur serious damage by the continued uncontrolleddischarge of steam to the condenser. Also the prior art methods do notprovide means to protect the thin walled tubes of the condenser frompotential damage due to debris or entrained water droplets in the steamentering the condenser.

In this embodiment of the invention, the steam is initially dischargedto the atmosphere to a temporary start-up silencer. The path of thesteam to the atmospheric silencer passes through a rapid opening valvethat is designed to fail in the open position.

In this embodiment of the invention, the rapid opening valve is actuatedby a pneumatic cylinder. The air supply to this pneumatic cylinder is atemporary air storage accumulator that is isolated from other plantsystem in such a manner as to provide assurance that sufficient airpressure and volume will be always available to actuate the exhaustvalve into the open position.

In this embodiment, during the initial generation of the dirtiest steamfrom the steam generator and steam piping, the most highly contaminatedsteam is exhausted from the system to the atmospheric silencer. Thisinitial period of steam discharge is typically coincidental to theinitial full-speed-no-load operation of the gas turbine. In thisembodiment of the invention, both plant condensate storage and thetemporary condensate storage tanks and pumps provided for by thisinvention are used to maintain a sufficient flow of make-up condensateto the steam generation equipment while the highly contaminated steam isbeing discharged to the atmosphere.

The present invention also provides for the addition of sufficientcondensate into the exhaust steam to generate a condition where thesteam is supersaturated with water droplets. Through the intimatecontact of the water droplets with the steam, the steam temperature willbe greatly reduced resulting in a significant reduction of thesolubility of silica in the steam. The entrained water droplets willalso agglomerate with particulate particles entrained in the exhauststeam flow. Salts that are also soluble in the steam will be washed fromthe steam by the entrained water droplets. Following the washing of thesteam, the present invention provides for the passage of the steamthrough a coalescer that will hold up the entrained dirty water dropletsto facilitate the separation of the contaminant laden water dropletsfrom the steam by means of a cyclonic separator. The combination of asteam wash means, by the injection of excess condensate into the highvelocity, high temperature steam; the passage of the washed steamthrough a coalescer means, to hold up the wash water effluent droplets,slowing their velocity and increasing their size as well as reducing theturbulence of the steam and a cyclonic separator means to separate theentrained wash condensate effluent from the exhaust steam is called the“steam conditioning equipment”.

The function of the cyclonic separator is enhanced by the design andpresence of the coalescer in the flow path immediately prior to theentrance of the cyclonic separator. The extended surface of thecoalescer, the increased steam flow cross section and the reduced flowpath wetted diameter through the coalescer have the effects of slowingthe water droplets entrained in the steam flow, increasing the dropletdiameters and reducing the turbulence of the steam as it passes throughthe coalescer. These conditions improve the ability of the cyclonicseparator to effectively remove the entrained wash condensate dropletsfrom the steam flow.

In this embodiment of the invention, the cleanliness of the steamentering the steam conditioning equipment is monitored by the insertionof a polished metal target into the inlet steam. The cleanliness of theinlet steam is also measured by the analysis of the effluent washcondensate from the cyclonic separator. A high concentration ofparticulate and non-particulate contamination in the wash condensateeffluent is an indication of the amount of contamination entrained inthe inlet steam.

Further, in this embodiment of the invention, the cleanliness of thesteam leaving the cyclonic separator, prior to its discharge to theatmospheric silencer, is also monitored by the insertion of a softpolished metal target at the outlet of the cyclonic separator. Theimpact of entrained solids or water droplets on the soft polishedsurface of the target would indicate that the exhaust steam is ofinsufficient cleanliness to allow its discharge to the condenser. Anunblemished polished target exposed to the exhaust steam flow wouldindicate that the steam cleanliness is suitable for discharge to thecondenser.

In addition to the above, a sample of the steam effluent from the steamconditioning equipment can also be passed through a condenser coil. Thecondensate sample produced by this condensing coil can then be analyzedfor the presence of non-particulate salts and silica.

In this embodiment, while the initial steam generated is vented to theatmosphere, steam may be introduced to the shaft seals of the steamturbine and a vacuum established in the condenser in preparation for theintroduction of steam to the condenser. In many cases, the normal plantdesign will provide for an auxiliary boiler that may be used to firstclean the steam path to the steam turbine shaft seals and then toprovide the necessary steam to those seals. Such an auxiliary boiler mayalso be used to provide motive steam to the steam jet ejectors that aretypically used to remove non-condensable gases from the condenser andestablish the necessary vacuum to allow for the safe operation of thecondenser.

In other cases where an auxiliary boiler is not provided for by thenormal plant design, a temporary boiler may be used to provide thenecessary seal steam and motive steam for the air removal from thecondenser.

In still other cases, a mechanical vacuum pump provided for by the plantdesign or a temporary mechanical vacuum pump obtain for thecommissioning may be used to generated the vacuum in the condenserrequired for the safe operation of the condenser.

In yet other cases the steam generated by the steam generator may beused to perform a service blow cleaning of the steam piping to the steamjet ejectors and the steam turbine gland steam supply piping. Once theselines have been blown clean, steam from the steam generator may be usedto provide the motive steam for the steam jet ejector equipment togenerate the necessary vacuum on the condenser and to provide seal steamto the steam turbine.

In still other cases, a separate high pressure steam conditioning unitmay be used to clean sufficient steam to provide sufficient clean steamfrom the steam generator to provide the necessary steam for the requiredseal steam flow to the steam turbine shaft seals.

Once the testing of the steam exhausting the steam conditioning unitindicates that the steam is sufficiently clean to be discharged to thecondenser, a warm-up valve is partially opened establishing a flow ofsteam from the exhaust of the steam conditioning unit through temporarypiping into the condenser.

In this embodiment, to establish a passage for the washed exhaust steamto the condenser, temporary piping is run to connect the outlet of thesteam conditioning equipment to the condenser. To distribute the exhauststeam into the condenser the temporary piping may be connected to theinlet of the normal plant bypass diffuser. If, as is normally the case,the sum of the cross sectional area of the perforations in this diffuseris too small to allow a low back pressure on the steam conditioningequipment, the diffuser will be modified to add additional open area onthe diffuser. In other cases, an additional temporary diffuser withgreater open area may be used either in place of the normal plant bypassdiffuser or as a supplement to the normal plant diffuser. In other casesthe steam conditioning equipment can be designed to be operated athigher a pressure to match the existing design pressure drop of theplant steam sparge tube. In any case, the backpressure from thedischarge of the steam through the diffuser at base load conditions ofthe gas turbine will be low enough to allow sufficiently high steamvelocities in the steam circuit to generate cleaning force conditions inexcess of 120% of those generated at normal base load conditions.

In this embodiment, a porous shield material would also be installed inthe condenser between the steam exhaust points on the diffuser and theexposed surface of the thin walled condenser tubes. In this embodimentthe shield material consists of woven wire mesh secured to an expandedmetal support sheet secured above the banks of condenser tubes. Thisshield layer would be arranged in such a manner as to require the steamflow into the condenser to pass through the porous shield before thesteam could directly impact the surfaces of the thin walled condensertubes. The woven wire, or other form of perforated porous media, wouldhave sufficient thickness to assure that any debris or water dropletsentrained in the steam discharged to the condenser would first have toimpinge on the porous media before striking the thin walled tubes. Theeffect of this porous media is to prevent the high energy impingement ofentrained particulate contamination or water droplets onto the surfacesof the thin walled condenser tubes. The thickness of the shield materialis preferably sufficient as to generate a few inches of water columnpressure drop on the steam as it passes through the porous shieldmaterial. In this way, the shield material will also act to supplementthe diffuser to assure a more uniform distribution of the exhaust steamwithin the condenser. The more uniform distribution of the steam withinthe condenser will reduce the potential for locally high flows of steamacross a few tubes. By a more uniform distribution of the steam thepotential for damaging localize heating of the condenser tubes or thegeneration of flow induced vibration of the thin walled tube ismitigated.

In this embodiment of the invention, once the temporary lines to thecondenser have been warmed by the steam, the flow of steam to thecondenser may be increased by further opening the warm-up valve to thecondenser. Experience has shown that the pressure of the steam chest ofthe condenser will increase somewhat with the initial introduction ofsteam to the condenser. By slowly introducing and then slowly increasingthe flow of exhaust steam to the condenser, the condenser air removalsystem will be able to control the condenser pressure within the normaldesign limits.

In this embodiment, once a continuous flow of steam to the condenser hasbeen establish, a rapid opening valve between the exhaust of the steamconditioning unit and the condenser is opened. In this embodiment of theinvention, the path of steam to the condenser passes through a rapidclosing valve that is designed to fail in the closed position. In thisembodiment of the invention the actuator on this valve is a pneumaticcylinder that is also powered by a secure supply of compressed air froma temporary air accumulator with sufficient volume and pressure toassure the actuation of this valve into the closed position should itbecome necessary to quickly terminate steam flow to the condenser.

In this embodiment of the invention, once the quick closing valve on theflow path from the outlet of the steam conditioning unit has been openedthe warm-up valve to the condenser from the steam conditioning unit willbe closed.

Once the steam flow path from the exhaust of the steam conditioning unitto the condenser is established, the rapid opening valve from theexhaust of the steam conditioning unit to the atmospheric silencer willbe closed. In this embodiment of the invention, this rapid opening valveis also provided with a warm-up valve. This warm-up valve on the pipingfrom the steam conditioning unit to the atmospheric silencer will befully opened prior to the closing of the rapid action valve on the flowpath from the exhaust of the steam conditioning unit to the atmosphericsilencer. In this embodiment of the invention, the opening of thiswarm-up valve prior to the closing of the rapid actuation valvemitigates any sudden change in steam flow to the condenser.

In this embodiment of the invention, the warm-up valve from the outletof the steam conditioner to the atmospheric silencer is slowly closedonce the rapid actuator valve to the silencer is closed. The warm-upvalve to the silencer is left partially open to maintain a sufficientflow of steam to the silencer to prevent the accumulation of steamcondensate in this flow circuit.

In this embodiment of the present invention, the target assembly andsteam sample point on the exhaust piping of the steam conditioning unitare positioned in such a manner that they will still be functional forthe monitoring of the exhaust of the steam conditioning unit while thesteam is discharged to the condenser.

In this embodiment of the invention, the steam cleanliness exhaustingthe steam conditioning unit will continue to be monitored during thedischarge of steam to the condenser. Any indication of an unacceptablelevel of contamination in the steam would result in the diversion of theexhaust steam from the condenser back to the atmospheric silencer.

In this embodiment of the invention, the control circuit for thesolenoids that provide compressed air to the rapid actuation valves isconfigured to cause the valve to the condenser to close on loss of plantpower and the rapid actuated valve on the steam flow path to theatmospheric silencer to open. This control circuit may also beconfigured to automatically actuate the temporary steam flow controlvalves in the event that the flow of cooling water flow to the condenseris lost, the steam temperature or pressure to the condenser exceeds apreset limit or the flow and/or pressure of the condensate used to coolthe steam being discharged to the condenser drops below a preset limit.In this embodiment of the present invention, the rapid actuated valvesmay also be operated by a manual switch or button should the operatorsdetermine that steam flow to the condenser must be rapidly terminated.

Once the steam flow to the condenser has been established, condensatewill begin to accumulate in the hotwell of the condenser. Experience hasshown that the condensate accumulated from the initial steam wash of thecondenser tube surfaces will be highly contaminated with bothparticulate and non-particulate contamination. In this embodiment of thepresent invention, one or more temporary pumps are connected to thehotwell to allow the condensate collected in the hotwell to beextracted. The operating condition of the condenser under a vacuumrequires that these pumps have the capability of handling sufficientcondensate flow to support a sufficient flow of steam condensate toprovide for a substantial steam wash of the condenser tubes. Toaccomplish this these pumps must also have the capability of operatingat the required flows with very low net positive suction head. In thepresent embodiment of this invention this is accomplished by means oflarge diameter, centrifugal pump. The net positive suction head to thesepumps may be increased by the addition of a flow inducing nozzle in thehotwell oriented to the suction of the temporary condensate pump. Thiswater supplied to this nozzle is supplied from the high pressuredischarge of the plant condensate pumps. The momentum of the highvelocity water exiting this nozzle is transferred to the water at thesuction inlet to the temporary pump, increasing the velocity head of thewater entering the temporary pump suction.

The low net positive suction head operation of these temporary hotwellcondensate pumps may also be improved by installation of a mechanicalflow inducer on the pump impeller and by use of larger pumps operatingat low rpm.

In this embodiment of the present invention, the impeller and casingdesign of the temporary condensate pump is such that the pump(s) arehighly tolerant of particulate contamination. In addition in thisembodiment of the present invention, the suction piping to thesetemporary condensate pumps may be equipped with a duplex strainer oflarge mesh. These strainers are configured to allow one strainer to becleaned while the temporary condensate pump(s) continue to operate bymeans of the second strainer.

In the present embodiment of the invention, the temporary dischargepiping from the temporary condensate pumps installed to take suctionfrom the condenser is initially routed to waste. The initial condensatethat is highly contaminated with both particulate and non-particulatecontamination is exhausted from the steam cycle. The same temporarycondensate storage tanks and pumps used to make-up sufficient condensateflow to the steam generator will continue to supply the requiredcondensate flow to support the operation of the steam generator whilethe highly contaminated condensate from the condenser is discharged fromthe steam cycle.

Experience has shown analysis of the condensate from the initial steamwash of the condenser will show that after a short period of time thelevels of both particulate and non-particulate contamination will beginto rapidly decrease. In the present embodiment of the invention, oncethe levels of contamination drop to a level that make condensatetreatment practical, the discharge of the condensate pumps takingsuction from the condenser hotwell are aligned to a set of filters thatwill remove particulate contamination larger than 20 microns from thecondensate. By removal of larger particle contamination from thecondensate, plugging of critical condensate and boiler feedwater valvetrim is prevented. Removal of the larger particles also preventsexcessive fouling of the condensate and boiler feedwater pump suctionstrainers. Removal of the large particles also prevents fouling of ionexchange resin beds or other water treatment equipment that may be usedto further treat the condensate to remove non-particulate contamination.

As the flow of cleaned condensate from the condenser hotwell isestablished, the flow of condensate from both the plant condensatestorage system and the temporary condensate storage and pumping systemprovided to make-up sufficient condensate flow until the returncondensate from the condenser is available for use will be removed fromservice. The temporary condensate storage tank and pumping capacity willbe maintained in such a manner as to provide an immediate supply ofcondensate to the steam wash and exhaust conditioning equipment shouldthe normal plant systems fail for any reason. In the present embodimentof the invention, this is accomplished by continuing the operation orthe temporary make-up condensate pumps in a minimum flow configurationwith a check valve between the discharge header of the temporarycondensate make-up pump(s) and the normal higher pressure dischargeheader of the plant condensate system. In this manner, with the failureof the plant condensate system for any reason, the discharge pressure ofthe temporary condensate make-up pump(s) will overcome the check valveand supply needed condensate to the critical steam temperature services.To assure the continuous operation of the temporary condensate make-uppump(s), at least one of the make-up pump(s) will be powered by a dieselengine driver or an electric motor powered from a secure power supplyseparate from the plant electrical system.

In the current embodiment of the invention, once the flow of condensatefrom the condenser has been established the load on the gas turbine maybe increased. Experience has shown that the flow of steam condensatefrom the condenser can be typically achieve by the time the normalcommissioning activities at full-speed-no-load of the gas turbine andthe initial synchronization checks of the gas turbine at low loads arecomplete.

Once the load on the gas turbine is increased to allow for the normalcommissioning of the gas turbine, the steam flow to the condenser willincrease proportionally.

Experience has shown that once the steam flow from the steam generatorand steam piping reach significant levels (at a gas turbine load of 20%or greater), the cleaning effectiveness of the steam flowing through thesteam generator superheater and the steam piping will be enhanced by theinjection of chemically treated condensate into the high velocity steamflow. As previously described, the injected condensate will form anannular mist flow regimen inside the steam path from the steam generatorto the connection point of the temporary piping near the steam turbineinlet. The beneficial effect of this condensate injection is monitoredby the target sample at the inlet of the steam conditioning unit as wellas the analysis of the effluent wash water from the steam conditioningunit. The injection of the chemically treated condensate into variouspoints in the system is continued from different injection points alongthe steam path between the steam generator and the temporary connectionpoint at the steam turbine. From the temporary connection point at thesteam turbine the dirty exhaust steam is routed by temporary piping tothe steam conditioning unit. Prior to the entrance of the dirty exhauststeam to the steam conditioning unit, the steam is sampled to monitorthe cleanliness of the steam exhausting the steam path. A polished metaltarget is used to determine the presence of particulate contaminationthat may be entrained in the exhaust steam. A steam sample is alsocondensed by means of a sample cooler and the steam condensate analyzedfor the presence of silica, ions that elevate the cation conductivityand other salt contamination in the exhaust steam.

Experience has shown that with operation of the steam generator at thehigher loads experienced during the burner tuning of the gas turbine,higher steam temperatures and steam flows are experienced. With eachsuccessive increase in load, the concentration of solid particle andnon-solid particle contamination in the exhaust steam is achieved.Experience has also shown that the addition of the chemically treatedcondensate into the high velocity steam also has the effect ofincreasing the concentration of contamination measured in the exhauststeam prior to the steam conditioning unit. Experience has also shownthat with time at the highest steam flow and temperature conditions, andafter successive cycles of chemically treated condensate injection intothe high velocity steam, the concentration of contamination in theexhaust steam will begin to decline. The simultaneous activities of gasturbine burner tuning and the removal from the steam path of bothparticulate and non-particulate contamination is continued until thesteam sample analysis indicates that the steam exhaust meets the bothparticulate and non-particulate steam cleanliness requirementsestablished for this stage of the commissioning for the steam paththrough the steam generator and steam piping to the steam turbine.

Past experience has shown that the exhaust steam from the steamgenerator and steam piping will be effectively clean by the time theburner tuning of the gas turbine is complete and the continuous baseload operation of the gas turbine for the flushing of the gas supplylines to the burners is begun. During the extended base load operationperiod, the addition of chemicals to the steam and condensate willcontinue to further enhance the removal of silica and othernon-particulate salt contaminates. The chemical treatment of the steamis also adjusted to generate a highly passive surface condition on themetal surfaces of the steam path. The passivation of the steam path isaccomplished by the addition of a volatile oxygen scavenger compound anda volatile pH adjustment compound to the steam and condensate.

The ability to facilitate the simultaneous tuning of the gas turbineburners up to base load operation and the decontamination of the steamcycle of both particulate and non-particulate contamination is theresult of the application of the steam conditioning equipment thatwashes the contaminated exhaust steam with clean condensate prior to thedischarge of that condensate to the condenser. Without the steamconditioning equipment, the condensate and entrained particulate andnon-particulate contamination would be carried over into the condenserresulting in potential damage to the condenser as well as the potentialdeposition of the contamination onto the metal surfaces of thecondenser. This process of the present invention is also facilitated bythe temporary equipment employed to treat the full flow of thecondensate generated by the steam condensation in the condenser toremove particulate and non-particulate contamination that has beenliberated from the condenser surfaces by the steam flush of thecondenser.

The level of cleanliness of the steam cycle uniquely achieved by thepresent invention is further facilitated by the operation of the gasturbine up to its base load firing rate. The firing rate of the gasturbine made possible by the preset invention is four to five timesgreater than that typically employed by previous steam cleaningprocesses that do not provide for the recovery of the exhaust steam inthe condenser. The higher steam temperatures and flows that are madepossible by the present invention accelerate the process ofdecontaminating the steam path of both particulate and non-particulatecontamination as well as to facilitate the simultaneous passivation ofthe steam path metal surfaces.

The present invention also provides for the decontamination andpassivation of the metal surfaces of the condenser and a means ofremoving the contamination generated from the steam flushing of thecondenser.

The present invention also provides for several unique means to preventpotential damage and potential fouling of the condenser metal surfaces.The steam conditioning equipment removes particulate and non-particulatecontamination from the exhaust steam prior to the introduction of theexhaust steam to the condenser. The temporary measures provided for bythe present invention also allow for the exhaust of the most highlycontaminated steam first generated by the steam generator as well as asystem to monitor both the particulate and non-particulate contaminationlevels at both the inlet and outlet of the steam conditioning equipmentprior to the admission of steam to the condenser. These temporarymeasures also provide a means to rapidly isolate steam flow from thecondenser should conditions arise that would cause potential damage bythe continued discharge of steam to the condenser. The present inventiontemporary measures also provide for separate overpressure protection ofthe temporary exhaust steam conditioning equipment and piping.

In this embodiment of the invention, the amount of high quality waterconsumed during the commissioning of the steam system is significantlyreduced by the recovery of the vast majority of the steam condensate.Once analysis of the exhaust steam shows that the levels ofcontamination have been significantly reduced, the steam conditioningwash condensate effluent may also be returned to the condenser hotwellto facilitate its treatment along with the condensate generated in thecondenser.

In a second embodiment of the present invention, a steam generator firedwith poultry liter on a grate and with an air cooled condenser may becommissioned in a similar fashion. In this embodiment of the invention,the cleaning of the steam path of both particulate and non-particulatecontamination is achieved at the same time that the fuel handling andfuel gas treatment equipment of the plant are being commissioned.

In the prior art, the steam path through the steam generator and steampiping was typically cleaned separately from the commissioning of thesolid fuel handling systems and the flue gas treatment systems. Therequired steam flushing of the air cooled condenser was also performedas a separate operation.

In this embodiment of the present invention, all of these activities areaccomplished at the same time. In this embodiment of the presentinvention, the temporary steam exhaust piping is designed to provide forthe initial venting of the first highly contaminated steam generated tothe atmosphere. As previously described, while the initial steamproduction is vented to the atmosphere, a vacuum is pulled on thecondenser. In this type of a plant, the initial steam production istypically accomplished by the firing of the steam generator usingnatural gas or propane. Due to the cost of these auxiliary fuelsrelative to the solid fuel specified for this type of plant, it ishighly beneficial to increase the firing rate sufficient to allowcommissioning of the solid fuel system.

Once the cleanliness of the exhaust steam has improved sufficiently toallow its discharge to the condenser, the steam flow is diverted fromthe atmospheric vent to the condenser in a similar fashion to thatpreviously described. After the steam exhaust has been diverted to thecondenser, the firing rate of the steam generator may be increased tothe point that solid fuel firing may be commenced and the use of theauxiliary fuels terminated. From this point forward the solid fuelhandling system and flue gas conditioning equipment may be tune up tothe base load firing condition.

In this embodiment of the present invention, chemically treatedcondensate is also injected at multiple points along the steam path tothe steam turbine in sufficient quantities as to generate an annularmist flow condition. The exhaust steam discharged to the condenser inthis embodiment is also tested for solid particle and non-solid particlecontamination as in the previous embodiment.

Due to the ability of the present invention to capture and return thesteam condensate used to flush the steam circuits of the plant, it isfeasible to add sufficient volatile chemicals to the steam cycle duringthe contamination removal process of this invention to significantlyenhance the rate and degree of system cleanliness without the dischargeof high concentrations of the treatment chemicals to the atmosphere.

It is well known, for example, that the solubility of silica in steam issignificantly increased as the pH of the steam is increased. To increasesteam condensate pH from 9.0 to 10.0, the ammonia concentration in thesteam must be increased from approximately 0.3 to 10 milligrams perliter. In prior art practices; where large volumes of the steam arecontinuously discharged to the atmosphere it is not practical to add asufficient quantity of a volatile chemistry such as ammonia to achievesuch elevated concentrations. In the preferred embodiment of the presentinvention, ammonia concentrations well above 20 milligrams per liter inthe steam are possible to maintain without the discharge of steam withsuch elevated ammonia concentrations to the atmosphere.

The preferred embodiment of the present invention also provides for theaddition of high concentrations of volatile reducing agents that helppromote the passivation of the metal surfaces of the air cooledcondenser and other plant systems. Again with the capture of the steamduring the procedures described by the present invention, it becomespractical to apply higher concentrations of such passivation enhancingchemistries during process of removing both particulate andnon-particulate contamination.

The temporary piping in this embodiment of the present invention alsoprovides for the installation of a temporary connection from the steampiping immediately prior to the steam turbine inlet valve. Thisembodiment of the present invention also provides for the installationof temporary diffuser(s) into the exhaust duct of the air cooledcondenser. The temporary piping and equipment installed for thisembodiment of the present invention also provides for the injection ofsufficient volumes of clean condensate into the exhaust steam togenerate an excess of water droplets that by contact with the exhauststeam will wash the steam of both particulate and non-particulatecontamination.

In this embodiment of the present invention, the separation of theparticulate and non-particulate contamination is accomplished by thedischarge of the steam through the temporary diffuser(s) into theexhaust duct of the air cooled condenser. This duct has a large diameterand sufficiently reduces the velocity of the exhaust steam to allow forthe separation of the excess wash condensate from the exhaust steam thatis conveyed by the duct to the condenser tube sections some distancefrom the steam introduction point.

In this embodiment of the present invention, the contaminated condensateseparated from the exhaust steam is collected in the drain pot on theexhaust duct. Temporary pumps with suction strainers connected to thisdrain pot are used to initially remove the highly contaminatedcondensate from the exhaust duct and discharge it to waste.

In this embodiment of the present invention, temporary condensatestorage and temporary condensate pumps and piping are also provided toprovide sufficient make-up condensate to the steam generator while theinitial highly contaminated steam is being exhausted to the atmosphere.This embodiment of the present invention also provides for the a meansto discharge to waste the initial highly contaminated condensate that isreturned from the air cooled condenser exhaust duct drain pot as well asthe initial condensate returned from the condenser sections. Once theexcess wash condensate from the exhaust duct has become clean enough toeconomically treat, this condensate is then diverted from waste to the atemporary condensate treatment system.

In this embodiment of the present invention, sufficient pump capacityand temporary condensate treatment equipment is provided with thecapacity to treat the volume of condensate generated by the condenser atthe base load operation of the steam generator combustion system.

This embodiment of the present invention also provides for theinstallation of rapid closing and rapid opening valves to allow steamdischarge to the air cooled condenser to be terminated should conditionswarrant such termination to protect the air cooled condenser fromdamage. The operation of these valves and the overpressure protectionequipment is the same as that described above.

The present embodiment of this invention allows for the commissioning ofthe solid fuel systems and flue gas treatment systems of this type ofsteam generator as well as the commissioning and steam flushing of theair cooled condenser system simultaneously with the cleaning of thesteam path through the steam generator and steam piping to the steamturbine.

In yet another embodiment of the present invention, a pulverized coalfired steam generator with water cooled condenser is commissioned in asimilar manner as described above. As applied to a pulverized coal firesteam generator, the present invention allows the use of much lessexpensive solid fuel to be used to fire the steam generator during thesteam cleaning program. As described above the temporary systems areprovided to allow at least one coal mill at a time to be operated atbase load condition. As with the previous embodiments of the presentinvention, this allows the removal from the steam path of bothparticulate and non-particulate contamination simultaneous to thecommissioning of the steam generator combustion systems and the flue gastreating equipment. The ability to operate the steam generator atsufficient loads as to allow the coal handling systems, the coalpulverizers, the combustion air systems, the flue gas treatment systemsand the fuel ash handling systems to be commissioned providessubstantial savings in the amount of time, water and fuel used for thecommissioning of the plant when such commissioning performs the steampath cleaning function separate from the other commissioning activities.

As with the previous embodiments of the present invention, theembodiment of the present invention to a pulverized coal fire steamgenerator will also make use of a means to wash contamination from thesteam prior to the admission of the steam to the condenser, the use ofchemically treated condensate injected into the steam to effect theformation of an annular mist that enhances the cleaning effectiveness ofthe steam for both solid particle and non-particulate contaminationremoval and the treatment of the steam condensate used for thismulti-purpose cleaning activity collected from the condenser prior toits return to the steam generator at flow rates sufficient to performthe normal commissioning activities of the steam generator combustionsystems.

In yet another embodiment of the present invention, exhaust steam fromthe steam system flush is also routed by means of temporary piping tothe steam coil air heaters of a coal fired or other solid fuel firedplant to perform a steam flush of these circuits at the same time theprimary steam cycle is being cleaned. In yet another embodiment of thisinvention, exhaust steam may also be conveyed through temporary pipingto the steam supply lines of the feedwater heater exchangers of thesolid fuel fired plant. The steam washing of the steam side of thefeedwater heaters promotes complete system cleanliness at the same timethe main steam circuits are being cleaned. The initial contaminatedcondensate from both the steam coil air heaters and the feedwaterheaters may be collected and initially discharged to waste. After thewash steam condensate to the steam coil air heaters and feedwaterheaters is no longer highly contaminated, the condensate from thesecircuits may be treated by the same temporary condensate treatmentequipment disclosed by this invention for treatment of the condensatefrom the steam turbine condenser. In addition to the benefit of cleaningthese additional steam circuits of both particulate and non particulatecontamination as part of an integrated cleaning and passivation process,the discharge of steam to the steam coil heaters and the feedwaterheaters has the added benefit of increasing the temperature of theexhaust path of the combustion gases from the boiler. Increasingtemperatures in the backpass of the boiler will help maintain theexhaust combustion gas above it dew point. Serious corrosion of themetal surfaces of the boiler backpass can occur if the combustion gas isallowed to cool below its dew point. In addition to the effect ofmaintaining the boiler backpass above the combustion gas dew point, thesimultaneous steam washing of the steam coil heaters and the feedwaterheaters also promotes higher combustion air temperatures. Highercombustion air temperatures provide for cleaner and more completecombustion of the fuels burned to support the combined steam cleaningand burner tuning effort. More complete combustion of the fuel reducesthe potential of contaminating the combustion gas path of the boilerwith unburned fuel and an increased rate of emissions to theenvironment.

Other objects, features and advantages will be apparent from thefollowing detailed description of preferred embodiments taken inconjunction with the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process flow schematic of typical prior art practice forsteamblow of piping in a power plant to remove particulate contaminationfrom the steam piping;

FIG. 2 is a process flow schematic of one embodiment of the presentinvention to provide for the simultaneous removal of particulate andnon-particulate contamination from the complete steam cycle;

FIGS. 3A and 3B are perspective views of the condensate wash andcoalescer apparatus used to remove particulate and non-particulatecontamination from contaminated steam prior to its discharge into thecondenser;

FIG. 4 is a cross-section view of the coalescer;

FIG. 5 is a perspective view of one embodiment of the steam/washcondensate cyclonic separator apparatus;

FIG. 6 is a process schematic of one embodiment of the rapid actingcontrol system for the diversion of steam from the condenser,

FIG. 7 is one embodiment of the porous shield apparatus used to protectthe thin walled condenser tubes;

FIG. 8 is side view of the one embodiment of the cyclonic separator,

FIG. 9 is one embodiment of a control system for steam admission to thecondenser from the exhaust steam system; and

FIGS. 10A, 10B and 10C are one embodiment of a porous metal shield,sparge tube and condenser tubes.

BRIEF DESCRIPTION OF PREFERRED EMBODIMENTS

The benefits of the present invention are based on the findings thatconsiderable savings of time, fuel and water are realized by applicationof the enhanced method described by this current invention. In thepreferred embodiment of the present invention both particulate andnon-particulate contaminations are simultaneously removed from the steamcycle of a steam turbine plant at steam flow and temperature conditionssignificantly greater than the operational conditions used to completeremoval of such contaminations from the steam cycle by means of theprior known art. In the prior art, the steamblow methods have beensolely focused on the removal of only the particulate contamination.Unlike the present invention, the operational conditions during thesteamblow were not manipulated to provide for the enhance removal ofnon-particulate contamination simultaneous to the operation of the unitto solely address removal of particulate contamination.

The present invention provides for the removal of such contaminations toa higher standard of cleanliness for both particulate andnon-particulate contamination under operational conditions that allowfor the concurrent performance of plant operational tuning requirementsthat must be completed prior to the commercial operation of the steamplant. The ability to perform significant plant combustion tuningsimultaneous to the decontamination of the steam cycle is previouslyunknown to the prior art. This feature of the present invention providesfor considerable savings of both time and fuel as the required removalof particulate and non particulate contamination and the tuningactivities of the plant combustion systems are completed simultaneouslyinstead of sequentially. With the higher operational firing rates thecleanliness of the steam cycle is achieved in fewer fired hours. Theability of completing particulate, non-particulate and tuning activitiessimultaneously reduces the amounts of fuel consumed as well as reducingthe duration of the commissioning activities.

In addition, the present invention facilitates the higher operationalfiring rates during the simultaneous removal of both particulate andnon-particulate contamination; and the required combustion tuningactivity by the recovery of the vast majority of the steam used toperform the decontamination. The present invention describes uniqueequipment and methods unknown in the prior art that provide for theremoval of harmful contamination from the exhaust steam prior to thedischarge of the exhaust steam to the plant condenser. In the presentinvention a means of washing the steam to separate both particulate andnon-particulate contamination from the steam prior to the condensationof the steam in the plant condenser is described. In addition thepresent invention also provides for redundant safety measures thatinsure the cleanliness of the steam discharged to the plant condenser aswell as providing means to protect the plant condenser fromtemperatures, pressures and flow conditions that may otherwisecompromise the condenser integrity. The methods and equipments describedby the present invention significantly reduce the amount of high qualitywater required to complete the decontamination of the steam cyclecompared to those practices known to the prior art. The recovery of thevast majority of the steam condensate provided for by the presentinvention significantly reduces the quantities of high quality waterrequired for the completion of the steam cycle decontamination as wellas the combustion process tuning. Under prior art methods, the inabilityof the new plant to generate a sufficient supply of high quality waterhas often extended the time required to complete both thedecontamination of the steam cycle as well as the initial tuning of thecombustion systems. The significantly reduced amounts of high qualitywater required by the present invention also provide the benefit ofreducing the cost of high quality water production.

The present invention also provides for the means to significantlyenhance the removal of non-particulate steam contamination by theintroduction of significant concentrations of volatile chemical agentsinto the steam. As provided for in the present invention, chemicalagents are added to the steam to accelerate removal of harmfulnon-particulate contamination from the steam cycle. The application ofsignificant concentrations of chemical agents to enhance removal ofnon-particulate contaminations from the steam cycle is unknown in theprior art. The removal of non-particulate contamination from the steamcycle is not addressed in the prior art. In the prior art methods, steamor compressed air used for the removal of particulate debris from thesteam cycle is vented to the atmosphere. The environmental impact andcost of the atmospheric discharge of chemically treated steam or airprecludes such practice from the prior art methods. It is a uniquefeature of the present invention that the removal of non-particulatecontamination is not only addressed by chemically enhanced. The presentinvention makes this possible by the recovery of both the steam andvolatile chemicals used to enhance non-particulate decontamination bydischarge of the chemically treated steam to the plant condenser inwhich both the steam and volatile chemicals are then condensed andeventually returned to the steam cycle.

While the present invention will be described with reference to acombined cycle power plant configuration, it is to be understood thatthis invention is applicable to other power plant configurationsincluding but not limited to pulverized coal type boilers, fluidized bedtype boilers, grate type boilers and other types of power plantsequipped with condensing steam turbines.

Referring now to FIG. 1, 1 is a combustion gas turbine generator (CTG)that when operated generates a flow of exhaust combustion gas that isdischarged through a duct 2 to pass across a series of tubular coilsections 3 typically described as a Heat Recovery Steam Generator(HRSG). In the HRSG, heat from the combustion gas preheats water,generates steam and superheats the steam in the various coil sections.Once depleted of waste heat, the exhaust combustion gas is discharge tothe atmosphere through a stack 4. In a typical installation,high-pressure steam from the HRSG is conveyed by piping 5 to ahigh-pressure steam turbine 6. Admission of steam to the steam turbineis regulated by stop and control valves 7. The mechanical energygenerated by the high-pressure steam as it expands through the steamturbine is used to power a generator 8 connected to the steam turbineshaft.

In a typical combined cycle installation, the steam exhausted from thehigh-pressure steam turbine is conveyed by piping 9 back to the HRSG tobe reheated. Piping 10 from the intermediate-pressure section of theHRSG may add additional steam to the flow of exhaust steam from thehigh-pressure turbine prior to the reheat section of the HRSG. Uponleaving the HRSG reheat section the reheated steam is conveyed by piping11 to the intermediate-pressure section 12 of the steam turbine.Admission of the reheated steam to the intermediate stage of the steamturbine is regulated by stop and control valves 13.

Steam that exhausts from the intermediate-pressure section of the steamturbine is conveyed by piping 14 to the low-pressure section 15 of thesteam turbine. Low-pressure steam piping 16 is used to conveylow-pressure steam produced by the HRSG to the low-pressure turbine.Admission of low-pressure steam to the low-pressure steam turbine isregulated by stop and control valves 17.

In normal operation, steam exhausting from the low-pressure turbineenters a large heat exchanger (condenser) 18 where it is condensed towater. Although there are several types of condensers, a common designcontains a large number of small diameter tubes 19 through which coolingwater is passed. The steam condensate from the condenser falls into thehotwell 20 situated below the condenser. Condensate pumps 21 returncondensate from the condenser to the HRSG 3 by means of condensatesystem 22. Suction strainers 23 at the suction of the condensate pumps21 remove particulate contamination from the condensate fed to the pumpsfrom the condenser hotwell 20. Removal of this particulate contaminationis required to prevent damage to the condensate pumps 21 and othercomponents of the condensate system 22.

In normal operation, additional mechanical energy is extracted from thesteam by the steam turbine by maintaining a vacuum on the condenser. Thevacuum on the condenser is maintained either by mechanical vacuum pumpsor by steam jet ejectors 24. To prevent damage due to excessivepressures and temperatures, condensers are normally designed to allowsteam admission only after a sufficient vacuum is created in thecondenser.

To prevent damage and contamination of the steam turbine components, thestop and control valves 7, 12 and 17 are kept closed until it is assuredthat the steam is free of harmful particulate and non-particulatecontamination. In the example prior art steamblow practice shown; thecoiled sections of the HRSG 3 that superheat the steam and the piping 5,9, 10, 11 and 16 used to transport the steam between the HRSG and thesteam turbine sections 6, 12 and 15 are flushed with high velocity flowsof steam through temporary fixtures and piping 25, 26, 27 and 28 to theatmosphere. To flush particulate debris from the high-pressure piping,steam is typically diverted from the high-pressure stop valve 7 throughtemporary fixtures and piping 25 to the atmosphere. To flush particulatedebris from the intermediate-pressure steam system, temporary piping 26is installed to divert high-pressure steam to the steam piping 9 used toconvey exhaust steam from the high-pressure steam turbine back to theHRSG 3 steam reheat section. The steam that passes through the reheatsection of the HRSG 3 and on to the intermediate stop and control valve13 through the hot intermediate steam piping 11 is also diverted to theatmosphere through temporary fixtures and piping 27 to the atmosphere.Temporary fixtures and piping 28 are also used to divert steamcontaminated with particulate material from the low-pressure stop valve17. Where convenient, the steam exhaust piping 25, 27 and 28 may becombined into a single exhaust system.

This temporary diversion of the particulate contaminated steam istypically continued until highly polished metal targets 29 inserted intothe steamblow exhaust indicate that the exhausting steam is free ofsignificant particulate contamination. Particulate contaminationentrained in the high velocity steam that is discharged from thetemporary steam exhaust piping 25, 27 and 28 will impact the surface ofthe highly polished metal target leaving an impression on the polishedsurface. Periodically the highly polished targets will be removed andexamined to determine the continued presence of particulatecontamination in the exhausting steam. The prior art does not providefor a means of measuring the concentration of non-particulatecontamination in the exhausting steam at the same time that particulatecontamination is being removed.

Prior art practices often include the addition of low quality servicewater to the exhausting steam after the target insertion point to cooland decelerate the steam that is exhausted to the atmosphere. Thissteamblow activity will frequently require several days to more than aweek to complete.

The discharge of large volumes of steam required to perform such a highvelocity steam flush requires the supply of substantial volumes of highpurity water for the duration of the steamblow. Typically the combustiongas turbine 1 is operated only at a rate sufficient to generate thesteam flow conditions that satisfy the steam turbine manufacturers steamflushing requirements. These rates are normally 20-30% of the maximumfiring rate of the combustion gas turbine. It is common for thesteamblow process to consume over one million gallons of high puritywater.

Once the steam is free of particulate contamination, the steamblow isterminated and the plant piping is reconfigured to the normal operatingarrangement. Once the plant is restored to its normal configuration, thecombustion gas turbine generator 1 will again be operated. In a typicalinstallation, valves 7, 12 and 17 will remain closed to preventadmission of steam to the steam turbine sections until testing of thesteam for non-particulate contamination shows that the steam quality isof acceptable purity to be safely admitted to the steam turbine. Duringthis period, steam generated by the high-pressure section of the HRSGinto the outlet piping 5 is diverted through conditioning valve 30 tothe high-pressure steam turbine exhaust piping 9 that returns steam tothe HRSG 3 to be reheated. To regulate the temperature of thehigh-pressure steam passing through valve 30, high purity water is addedto the steam. This is necessary to lower the temperature (condition) thesteam to prevent overheating of the high-pressure steam turbine exhaustpiping 9 and the reheater section of the HRSG 3.

The reheated steam from the HRSG 3 that cannot be safely admitted to thesteam turbine intermediate-pressure section due to the presence ofnon-particulate contamination is typically vented to an atmosphericsilencer 31 through a vent valve 32. If the steam vented through thereheater vent valve 32 is not free on particulate contamination, thesteam passages through this valve may be fouled or damaged. Once it isdeemed safe to discharge steam to the plant condenser 18, and thecondenser is under a sufficient vacuum, a reheat steam conditioningvalve 33 is opened to bypass steam to the condenser 18. To protect thecondenser from the high temperatures of the reheated steam, theconditioning valve 32 is designed to add sufficient condensate into thebypassed steam to lower the temperature of the steam entering thecondenser to a level consistent with the condenser's design limits. Thereheat steam that is bypassed to the condenser is distributed above thelarge number of condenser tubes by a perforated sparge tube 34.

Steam containing non-particulate contamination not suitable foradmission to the steam turbine is often bypassed to the condenser for anextended period of time until the levels of non-particulatecontamination are reduced to levels that meet the steam turbinemanufactures requirements. If the steam bypassed to the condenserthrough the conditioning valve 33 is not completely free of particulatecontamination, the bypass conditioning valve 33 and the distributorsparge tube 34 may be damaged or fouled. The condenser tubes 19 may alsosuffer erosion damage due to the impingement of high velocityparticulate contamination onto the condenser tube surfaces.

Low-pressure steam generated by the HRSG 3 and conveyed to thelow-pressure section of the steam turbine 15 by piping 16 may also bediverted directly to the condenser until the levels of non-particulatecontamination in the steam meet the cleanliness requirements of thesteam turbine manufacturer. This diversion is made through yet anotherbypass conditioning valve 35. The low-pressure steam that is bypassed tothe condenser is distributed above the large number of condenser tubesby a second perforated sparge tube 36. Condensate is added to thelow-pressure steam that is diverted through the bypass valve 35 toreduce the temperature of the low-pressure steam bypassed to thecondenser. If the steam bypassed to the condenser through theconditioning valve 35 is not completely free of particulatecontamination, the bypass conditioning valve 35 and the distributorsparge tube 36 may be damaged or fouled. The condenser tubes 19 may alsosuffer erosion damage due to the impingement of high velocityparticulate contamination onto the condenser tube surfaces.

The exterior surfaces of the large number of condenser tubes 19 in thecondenser are not flushed during the steamblow used to removeparticulate contamination from the steam sections of the HRSG 3 and thesteam piping 5, 9, 10, 11, and 16. Due to the large metal surface areaof the condenser tubes 19 a significant amount of particulate andnon-particulate contamination may be entrained in the condensatesupplied to the condensate pumps 21 from the condenser hotwell 20. Thesuction strainers 23 of the condensate pumps are designed to removeparticulate contamination that may damage the condensate pumps andsensitive components of the condensate system 22. Depending on the caretaken to manually flush the condenser 18, condenser tubes 19 and thecondenser hotwell 20, the suction strainers 23 of the condensate pumps21 may have to be clean numerous times. The combustion gas turbinegenerator 1 consumes significant quantities of fuel gas during theextended period of time required to purge non-particulate contaminationremaining in the steam cycle following the completion of prior art typesof steamblows.

The method of the present invention provides for an improved means forsimultaneously removing both particulate and non-particulatecontamination from the plant steam cycle as the combustion gas turbinegenerator 1 is operated at a firing rate that also allows simultaneoustuning of the combustion gas turbine burners. The method by which thisis accomplished is illustrated by reference to FIG. 2 that representsthe same general arrangement of a combined cycle power plant asillustrated in FIG. 1.

Referring to FIG. 2, in the preferred embodiment of the presentinvention, temporary piping 37 is installed at the end on thehigh-pressure steam piping 5 to divert steam from the high-pressuresteam turbine 6. As in prior the prior art, this diversion may beaccomplished by means of a special fixture installed at thehigh-pressure steam stop valve 7. Although such fixtures may be usedwith the present invention, these fixtures typically represent asignificant restriction to the flow of steam. Due to the greaterquantities of steam generated during the operation of the combustion gasturbine generator 1 during the application of the present invention, thepreferred embodiment of the present invention is to connect thetemporary piping directly to the high-pressure steam piping a shortdistance prior to the stop valve 7. This can be accomplished byconnection of the temporary piping to a drain pot on the high-pressuresteam piping 5 used to remove condensate from the piping. In most modernpower plant designs, the maximum design temperature of the high-pressuresteam will exceed 1,000° F. In prior art steamblow methods shown in FIG.1, due to the lower rates of operation of the combustion gas turbinegenerator during the steamblow, the temporary piping 26 is oftenconstructed of carbon steel material.

In the preferred embodiment of the current invention, the combustionburners of the combustion gas turbine generator will be tunedsimultaneously with the performance of the steamblow. During suchtuning, the temperature of the steam during the steamblow will typicallyreach the maximum design temperature of the high-pressure steam piping.As a result it is necessary for the first section of the temporarypiping 37 used with the present invention to be constructed of hightemperature alloy piping capable of safely operating at the elevatedsteam temperatures and flows generated as a result of the full loadoperation of the combustion gas turbine generator 1. Under the presentinvention, in situations where the HRSG 3 has been added to an existingcombustion gas turbine generator 1, the present invention also allowsfor the base load operation of the combustion gas turbine generator 1while the steamblow is being completed. The combustion gas turbinesgenerally operate much more efficiently at base load than at the loweroperating rates commonly used by prior art steamblow practices. n apreferred embodiment of this invention, the use of allow steel for thetemporary piping 37 may be avoided by installation of a temporarycondensate injection point 142 on the high pressure steam piping 5 priorto the high pressure stop valve 7. Injection of sufficient condensate atthis point will cool the exhaust steam sufficiently to allow the safeuse of carbon steel pipe for the temporary piping 37.

Once the steam enters the high temperature temporary piping 37 from thehigh-pressure steam header, a temporary attemperator 38 is used toinject condensate or boiler feedwater into the exhausting high-pressuresteam to further cool the steam to a temperature within the designlimits of the high-pressure steam turbine exhaust piping 9. When it isnot possible to install a condensate injection point 142 in the highpressure steam piping, it will be necessary for the first section of thetemporary piping 37 to be constructed of alloy steel. A short distanceof approximately 20 to 30 pipe diameters after the location of thistemporary attemperator 38, the material of the temporary piping 37 maybe changed from high temperature alloy piping to carbon steel piping.

Under the preferred embodiment of the present invention, the temporarypiping 37 will discharge the cooled steam exhausted from thehigh-pressure steam piping 5 into the high-pressure steam turbineexhaust piping 9. Under the preferred embodiment of the presentinvention, the temporary exhaust piping 37 will also have a tee equippedwith a valve 39 that can be used to discharge steam from this pointdirectly to the steam exhaust header 42. The arrangement of the tee issuch that solid particle contamination that is entrained in the steamthat exhausts from the high-pressure steam piping 5 will preferentiallybe discharged directly to the steam exhaust header 42.

In the preferred embodiment of the present invention, the valve on thetee 39 will be opened during the initial firing of the combustion gasturbine generator to insure that debris from the high-pressure steamsection of the HRSG 3 and the high-pressure steam piping 5 arepreferentially discharged into the steam exhaust header 42 rather thanthe high-pressure steam turbine exhaust piping 9.

The initial steam that exhausts from the high-pressure steam piping 5into the steam exhaust header 42 will be contaminated with highconcentrations of both solid particle and non-solid particlecontamination. In the preferred embodiment of the present invention, ahigh temperature target insertion device 43 will be positioned on thesteam exhaust header to allow the cleanliness of the steam exhaust to bedetermined. This device is similar in design to the target devices 29described in the earlier prior art. However due to the highertemperatures and higher steam flow rates generated by the preferredembodiment of the current invention, the target insertion device 43 mustbe constructed of high temperature alloy metallurgy to withstand theforces of the exhaust steam. The high temperature target insertiondevice 43 is used to determine the presence of particulate contaminationof the exhaust steam prior to the steam conditioning equipment 44, 45,46 and 58.

One of the primary objectives of the present invention is to wash theexhaust steam and sufficiently remove both entrained solid particle andnon-solid particle contamination from the steam to allow the safedischarge of the exhaust steam to the plant condenser 18. To do this alarge volume of high purity condensate is sprayed into the exhaust steamby one or more injection nozzles 44. Sufficient condensate is injectedinto the steam to lower the steam to the steam saturation temperature.In the preferred embodiment of the present invention, sufficientcondensate is injected by the spray nozzles 44 to cause the steam tobecome laden with fine droplets of condensate. In prior art steamblowtechnology; low quality service water is injected into the exhaust steamto decelerate the steam sufficiently to avoid a sonic discharge andexcessive noise at the exhaust point of the steam to the atmosphere. Inthe preferred embodiment of the present invention the steam flowconditions in the steam exhaust header are at a high velocity sufficientto promote turbulent mixing of the entrained condensate droplets withthe contaminated steam. The smaller particulate contamination and thesalts that comprise the non-particulate contamination entrained in theexhaust steam will become entrained in the liquid condensate droplets asthe liquid condensate droplets are vigorously mixed by the turbulence ofthe exhausting steam.

In the preferred embodiment of the present invention, a secondcondensate injection spray 45 may be position on the exhaust steampiping to insure that the exhaust steam contains a sufficient amount ofentrained water droplets to affect a thorough washing of the exhauststeam. Following the condensate injection sprays, the mixture of steamentrained water droplets and entrained solid particle contamination aredischarged into a coalescing section of the exhaust steam header 46. Across-sectional view of a preferred embodiment of the inlet of coalescersection is shown in FIGS. 3A and 3B.

In the preferred embodiment of the present invention, the inlet of thecoalescing section is divided into four flow channels of equal crosssectional area by metal plates 47. Situated behind these dividing plates47 is a piece of square grating 48 to which are attached a large numberof metal rods 49 of unequal length. The metal rods 49 are arranged suchthat the long axis of the rod is parallel to the flow direction of themixture of steam and the entrained condensate droplets. The coalescingsection of the steam exhaust header is connected to the exhaust headerpiping by means of a standard flanged joint connection 50.

A top view of the coalescing section of the steam exhaust header isshown in FIG. 4. The four channels defined by the dividing plates arealso constricted by additional metal plates 51 fixed to the inside wallsof the coalescer section to form four rectangular channels 52, 53, 54and 55 at the outlet of the coalescer section as shown in FIG. 5. Theends of the side plates are also shown in the outlet cross-section viewof the coalescer section of the steam exhaust header in FIG. 5. Theoutlet end of the coalescing section of the steam exhaust header isprovided with a standard pipe flange connection 63 with which it may bejoined to the inlet of the cyclonic separator section 58. Thecross-sectional area of the coalescer section is sufficient to maintainor even reduce steam velocities in spite of the flow area occupied bythe divider plates and the included metal rods.

In the preferred embodiment of the present invention, the surfaces ofthe metal rods 49 are rough so as to provide a large amount of surfaceupon which the condensate droplets and solid particle contaminationentrained in the exhaust steam will impinge and be held up. The largesurface area represented by the large number of rough rods included inthe coalescing section of the steam exhaust header has the effect ofsignificantly reducing the wetted diameter of the coalescing section. Asa result, the turbulence of the steam through this section of the steamexhaust header is significantly reduced. As a result of the impactbetween the entrained condensate droplets and the entrained solidparticle contamination on the rough rod surfaces and the reduction ofthe turbulence of the steam through the coalescing section of theexhaust steam header, the velocity of the entrained condensate dropletsand solid particles are reduced relative to the velocity of the steampassing through this section.

The length of the rods in each flow channel of the coalescing section isnot equal. Referring to FIG. 4, the rods with the longest length 56 arepositioned on the side of each flow channel that will be aligned withthe outer radius of each of the four inlet channels 59, 60, 61 and 62 ofthe cyclonic separator 58 into which the mixture of steam and entrainedcondensate droplets are discharged. Each succeeding row of rods isshorter with the shortest rods 57 in the flow channel positioned closestto the center of the cyclonic separator. This variation in the length ofthe rough rods provides a means of increasing the frictional resistancethat the surface of the rough rods imparts to the steam flowing throughthe coalescing section of the steam exhaust header with the effect thatthe velocity of the steam closest to the outer wall of the cyclonicseparator is reduced relative to the velocity of the steam closer to thecenter of the cyclonic separator. The lower steam velocity near theouter wall of the cyclonic separator provides for an improvedperformance of the cyclonic separator.

The impingement of the entrained condensate droplets and any solidcontamination entrained in the steam on the rough surfaces of the rodsreduces the velocity of the condensate droplets and the solidcontamination particles relative to the velocity of the steam passingthrough the coalescing section of the steam exhaust header. The roughsurface of the rods will further retard the velocity of the condensatedroplets with the result that the size of the droplets is increased. Thereduction of condensate droplet velocity and the particulatecontamination particles relative to the steam velocity and the increasesize of the condensate droplets improves the function of the cyclonicseparator 58 into which the steam, droplets and solid particlecontamination are discharged from the coalescing section.

A cross-sectional view of the inlet of the cyclonic separator section ofthe steam exhaust header is shown in FIG. 6. The four steam flow inletchannels 59, 60, 61 and 62 align with the four channels 52, 53, 54 and55 of the coalescing section of the steam exhaust header. The cyclonicseparator section 58 of the steam exhaust header is joined to thecoalescing section 46 of the steam exhaust header by means of a standardpipe flange connection 64.

In the preferred embodiment of the present invention, the cyclonicseparator section 58 of the steam exhaust header will consist of fourcylindrical barrel sections 65. The mixture of the steam, solid particlecontamination and the condensate droplets containing small particulatecontamination and salts that comprise the non-particulate contaminationenter each barrel section 65 tangentially at a high velocity.Centrifugal forces cause the solid particle contamination and condensatedroplets that contain both small solid particle contamination as well asnon-particulate contamination to collect on the outer wall of eachbarrel.

The contaminated condensate droplets and solid particulate contaminationentrained in the exhaust steam will drop to the bottom coned section 66of the cyclonic separator barrel 65. In turn the contamination will thendrop into a collection tank 67 positioned below the cyclonic separatorbarrels. In the preferred embodiment of the present invention, thecollection tank is equipped with a level indication device to show thelevel of contaminated water in the collection tank. The collection tankis also equipped with several flanged connections 69 from which thecontaminated condensate and particulate debris may be removed from thecollection tank.

The high velocity steam that tangentially enters the barrel section ofthe cyclonic separator is exhausted from the cyclonic section of thesteam exhaust header through a cylindrical exhaust tube 70 thatprotrudes into the top of each of the cyclonic separator barrels 65. Thesteam that exits each of the four barrel sections of the cyclonicseparator section has been separated from the entrained contamination bymeans of the centrifugal forces acting on the contaminated particles andcontamination containing condensate droplets. The steam that exits thefour sections of the cyclonic separator is collected in a common steamoutlet header 71. This exhaust header is equipped with a number ofstandard pipe flange connections 72 that provide a means of connectionthe steam outlet header to the remainder of the steam exhaust headersystem.

FIG. 7 is a top view of the cyclonic separator section of the exhauststeam header showing the same components from a different view. FIG. 8is a side view of the cyclonic separator.

Referring again to FIG. 2, in the preferred embodiment of the presentinvention, the condensate used to wash the exhaust steam that isseparated by the combined action of the coalescing section and thecyclonic separator section of the exhaust steam header system is removedfrom the cyclonic separator collection tank by means of a condensateremoval pump 73. The multiple drain connections 69 on the collectiontank 67 are used to supply the contaminated condensate through multiplestrainers 74 to the suction of the condensate removal pump. Thecontaminated condensate removed from the collection tank 67 of thecyclonic separator 58 is discharged to waste or recycled to a condensatepolishing system to be described latter. The level of non-particulatecontamination in the contaminated steam that exhausts from the plantpiping system is monitored by means of a sample point 75 on thecondensate removal system from the collection tank 67 of the cyclonicseparator. The samples taken from this sample point are monitored forthe presence of solids as well as cation conductivity, silica, sodiumand other contaminants that are detrimental to the proper operation andmaintenance of the steam turbine.

The cleansed steam that exhausts from the cyclonic separator commonsteam outlet header 71 will not contain solid particulate andnon-particulate contamination at levels harmful to the operation of theplant condenser 18 or other plant equipment. To confirm exhaust steamcleanliness is suitable for discharge to the plant condenser 18, atarget insertion device 76 is positioned at the outlet of the coalescingsection. Whereas the polished metal targets used to measure the steamcleanliness contaminated steam exhausted from the plant steam circuitswill be made of brass or steel, the target material inserted into thewashed exhaust steam is made from highly polished aluminum. The softsurface of the highly polished aluminum will show the presence of finesolid particle contamination entrained in the exhaust steam. Periodicinspection of the soft aluminum target confirms that the solid particlecontamination indicated by the targets inserted into the contaminatedexhaust steam at target injection point 43 positioned prior to the washcondensate injection, coalescer section and cyclonic separator sectionshas been successfully removed. The presence of non-particulatecontamination in the cleansed steam from the common steam outlet headeris also tested to determine the concentration for non-particulatecontamination by means of a sample point 77 at the outlet header of thecyclonic separator. In the preferred embodiment of the presentinvention, this sample point is equipped with a small heat exchanger tocondense the steam sampled to generate a liquid sample that may betested for harmful contaminants. The function of the condensate wash,coalescer section and cyclonic separator section in removing bothparticulate and non-particulate contamination from the exhaust steam ismonitored by comparison of the analytical tests performed on thecondensate samples taken from sample points 75 on the contaminatedcondensate removal system and sample point 77 on the cleansed exhauststeam outlet header.

In the preferred embodiment of the present invention, the cleansedexhaust steam that exits the cyclonic separator enters a clean steamexhaust manifold 78 at the outlet header of the cyclonic separatordevice. From this manifold the cleansed exhaust steam may be directed toone of several different flow paths. During the initial operation of theexhaust steam header system, the exhaust steam is directed to theatmosphere. In the preferred embodiment of the present invention thissteam is discharged through a silencer device 79 to the atmosphere byway of quick operating valve 80. A second flow path for the exhauststeam is provided by a bypass valve 81 that also provides a steam pathto the atmosphere. A third flow path for the exhaust steam is providedthrough quick operating valve 82 into temporary piping 83. In thepreferred embodiment of the present invention the temporary piping 83conveys the clean exhaust steam to the plant reheat bypass piping 84.The steam that enters the plant reheat bypass piping 84 will continue toa diffuser device 34 in the plant condenser 18. In a variation of thepresent invention, the temporary piping 83 may be connected directly tothe condenser 18 and a temporary diffuser installed specifically for thecommissioning of the steam system. A fourth flow path for the exhauststeam is provided by a bypass valve 85 that also provides a steam pathto the condenser 18. A fifth flow path for the exhaust steam from theoutlet of the cyclonic separator is provided by a pressure relief system86. This pressure relief system may consist of rupture disks, springloaded safety valves or other similar devices set to automatically openshould the pressure of the steam in the cyclonic separator outlet header78 exceed a preset design limit.

In the preferred embodiment of the present invention, the initial steamflow will discharge through valves 80 and 81 to the atmospheric silencer79. Steam flow to the condenser 18 will be prohibited by maintainingvalves 82 and 85 in the closed position. This flow arrangement will bemaintained until the cleanliness of the exhaust steam at the cyclonicseparator outlet header 78 can be confirmed by the samples taken fromsample point 77 and the target insertion point 76. The discharge of theexhaust steam to the atmosphere will also allow time for a vacuum to begenerated on the condenser 18 by the condenser vacuum system 24.

Once it is confirmed that the exhaust steam cleanliness meets criteriafor safe discharge to the plant condenser 18, and the condenser vacuumsystem 24 has reduced the pressure in the condenser to a level that iswithin the design limits of the condenser, the bypass valve 85 on thesteam flow path to the condenser is slowly opened to warm the temporarypiping 83 and the plant reheat bypass piping 84. The steam that passesthrough the bypass valve 85 will enter the condenser 18. The ability ofthe condenser vacuum system 24 to maintain a vacuum within the designlimits of the condenser 18 with the admission of steam to the condenseris also verified with the steam flow through the bypass valve 85.

Once it is confirmed that the exhaust steam cleanliness meets the designlimits of the condenser 18 and that the condenser vacuum system 24 ismaintaining a vacuum with the design limits of the condenser, the quickoperating valve 82 is opened increasing the flow of steam to thecondenser. Once full exhaust steam flow to the condenser is establishedthrough quick opening valve 82 the quick opening valve 80 to theatmosphere is closed. The bypass valve 85 is also closed. The bypassvalve 81 is left partially open to maintain a minimal steam flow to theatmospheric exhaust silencer 79 to keep this piping warm.

The safe operation of the condenser 18 requires that the temperature andpressure of the steam entering the condenser be maintained within thedesign limits of the condenser. The continued operation of the condenservacuum system 24 and the condenser coolant system 86 are critical tothat safe operation. Loss of the vacuum system or coolant system flowmay result in the rapid heating of the metal parts of the condenser withthe result that condenser components are damaged. Temperatures andpressures that exceed the design limits of the condenser 18 may alsoresult in thermal expansion of steam turbine components 15 in directcommunication with the condenser and result in damage to thosecomponents. An over pressure condition in the condenser may also causethe condenser safety relief system to fail.

To protect the condenser and other plant components from potentialdamage, the preferred embodiment of the present invention provides for ameans for rapid termination of steam admission to the condenser from theexhaust steam system. Referring to FIG. 9, the flow control valve 80 onthe flow exhaust steam flow path to the atmosphere is equipped with avalve operator 87 designed to rapidly open the valve 80 should the airsupply 88 to the valve pneumatic operator be discontinued. The airsupply 88 is provided through solenoid valve 89 from an air reservoirtank 90. The solenoid valve 89 is set to close in the event of aninterruption of electrical power to the solenoid valve. This would inturn interrupt the air supply to the rapidly operating valve 80 causingit to open and release the exhaust steam to the atmosphere.

In similar fashion the control valve 82 on the exhaust steam flow pathto the condenser 18 is equipped with a valve pneumatic operator 91designed to rapidly close should the air supply 92 to the pneumaticoperator be discontinued. The air supply 91 is provided through solenoidvalve 93 from an air reservoir tank 90. The solenoid valve 93 is set toclose in the event of an interruption of electrical power to thesolenoid valve.

The compressed air is supply 94 to the air reservoir tank 90 mayoriginate from the normal plant compressed air system or from atemporary air compressor supplied for that purpose. The air inlet to theair reservoir tank 90 is equipped with a check valve 95 designed toprevent depressurization of the compressed air reservoir tank should thecompressed air source 94 become compromised.

Electrical power is supplied to the solenoid valves 89 and 90 byelectrical wiring 96. Electrical switches 97 and 98 located at aposition convenient to the steam exhaust system, may be used to manuallyoperate the rapid closing valves 80 and 82 locally. This feature allowsfor the testing of the system prior to the start of the operation, thelocal control of the system manually for the initial introduction ofexhaust steam to the condenser, and local operation of the valves in theevent of a safety or operational problem.

The process of removing both particulate and non-particulatecontamination from the steam systems of the plant may take a number ofhours to complete. In the preferred embodiment of the present invention,an automated control system is used to monitor the condition of theexhaust steam, the condenser and other systems to assure the safety ofthe condenser. This control system is designed to automaticallyinterrupt the electrical power supply to the solenoid valves 89 and 93if certain critical design conditions are not maintained. Sensors thatmonitor the exhaust steam pressure 99, the exhaust steam temperature100, the condenser pressure 101, the flow of coolant to the condenser102 and the pressure of the compressed air reservoir tank 103 areconnected to a controller that will interrupt the electrical powersupply to the solenoid valves 89 and 90 should the condition of any ofthese variables deviate from preset design limits. In the preferredembodiment of the present invention, a master power supply switch isalso located in the plant control room to allow the power plantoperators the ability to stop steam admission to the condenser for anyreason.

Again referring to FIG. 2, as previously described, the cleansed exhauststeam that is discharged to the condenser is distributed in thecondenser by means of an internal distributor device 34. These steamdistributor devices normally used to discharge reheat steam within thecondenser frequently consist of a perforated section of pipe. The numberand size of the perforations in this distributor pipe are designed togenerate a specified backpressure on the reheat bypass valve 33. It iscommon for the size and number of perforations in the distributor device34 to be limited to result in a backpressure of 100 psig or more at theoutlet of the reheat bypass control valve 33. A higher backpressure onthis valve will allow the use of a smaller bypass valve and bypasspiping 84. A higher backpressure on the exhaust steam during theoperation to clean the steam system of particulate and non-particulatecontamination is not beneficial, as higher pressures will reduce steamvelocities in the steam paths being cleaned. Higher steam velocitiesimprove the ability of the exhaust steam to entrain contamination intothe steam.

In the preferred embodiment of the present invention, the steamdistribution device 34 in the condenser is modified to reduce thebackpressure on the exhaust steam header system and the plant steampaths to facilitate a more rapid removal of both particulate andnon-particulate contamination from the steam path. An increase in thenumber and size of the perforations in a modified steam distributordevice will reduce the pressure drop of the steam as it expands throughthe perforations and also reduce the potential for the generation ofhigh-energy sonic disturbances that may otherwise induce harmfulvibrations in the thin walled condenser tubes 19.

Where it is not practical or desirable to modify the permanent steamdistribution device 34 to reduce backpressure, a temporary steamdistribution device may be installed.

Although the steam leaving the cyclonic separation section 58 of theexhaust steam system can be sampled by means of the soft aluminum targetinsertion device 76, additional contamination origination in thetemporary exhaust piping 83 and the plant reheat bypass pipe 84 maybecome entrained in the steam exhausted to the condenser 18 through thedistributor 34. In addition, any upset condition in the operation of theexhaust steam condensate wash, coalescer and cyclonic separator sectionsmay result in a short term exposure of the thin walled condenser tubes19 to the erosive effects of entrained high velocity condensate dropletsand/or particulate contamination. Although the temporary piping 83 andthe reheat bypass piping 84 may be manually cleaned and inspected tominimize the potential for damage to the thin walled condenser tubes 19due to such entrain materials, in the preferred embodiment of thisinvention an impingement shield is installed in the condenser to protectthe condenser tubes from damage.

Referring to FIGS. 10A, 10B and 10C, the preferred embodiment of thepresent invention provides the installation of a porous metal shield 104between the steam distributor device 34 the top row of the thin walledcondenser tubes 19. In one potential variation of the invention, theporous metal shield consists of one or more layers of woven wire cloth105 fixed to an expanded metal support 106. The frame is in turn fixedto metal brackets 107 that are fixed to the condenser tube supportsheets 108. Normally the entry port available to gain access to theinterior of the condenser has a limited diameter. As a result it isnecessary that the porous shield device be assembled inside thecondenser from components that are able small enough to fit through theentry port. The typical assembly of the porous shield device is shown inthe detail of FIG. 10A.

In addition to providing a surface upon which entrain particulatecontamination and water droplets may impinge, the porous metal shieldalso generates a small amount of pressure drop as the steam passesthrough the shield. As an added benefit, the shield therefore helpsdistribute the exhaust steam more uniformly across the top surface areaof the condenser tubes. The uniform distribution of the exhaust steamover the top of the condenser tubes prevents localized areas of highvelocity steam that may otherwise cause harmful condenser tubevibration.

Again referring to FIG. 2, the exhaust steam that is distributed overthe thin walled condenser tubes 19 is cooled by the flow of the coolant86 circulating through the tubes. As the steam cools, it condenses. Thecondensed steam falls to the bottom of the condenser and collects in thecondenser hotwell 20. The large number of condenser tubes 19 has a largeamount of surface area. During construction of typical power plants, thelarge surface area of the condenser tubes is often contaminated withdust, dirt and construction debris. The tight clearances between thelarge number of small diameter tubes makes it difficult to manuallyclean or flush these surfaces prior to the initial introduction of steamto the condenser. As a result, it is common for the initial condensategenerated in the condenser to contain high concentrations of bothparticulate and non-particulate contamination. Prior art steamblowpractices for the removal of particulate contamination do not provide ameans of effectively removing such contamination from the condensatecollected in the hotwell.

In the preferred embodiment of the present invention, a means isprovided to address the contamination in the condensate initiallycollected in the condenser hotwell 20. A temporary pump 109 that iscapable of pumping condensate contaminated with small particulatecontamination is connected to the hotwell 20 by temporary suction piping110. A large temporary porous screen 111 is install in the hotwell 20 toprevent contamination that is too large for the temporary pump 109 tohandle from entering the temporary suction piping 110. Due to the verylow pressure in the hotwell as a result of the vacuum drawn on thecondenser 18 by the vacuum system 24 the net positive suction head tothe temporary hotwell pump is very low. In the preferred embodiment ofthe present invention, the net positive suction head to the temporaryhotwell pump 109 may be increased by the installation of a temporaryrecirculation line 112 from the discharge of the temporary hotwell pump.At the end of the temporary recirculation line, a nozzle is installed ina position to discharge a stream of high velocity condensate into thesuction of the temporary hotwell pump. The velocity of the recirculatedcondensate induces the flow of additional condensate from the hotwell 20into the suction of the temporary hotwell pump 109 increasing the netpositive suction head to the pump thus allowing the pump to functionproperly with a vacuum on the condenser.

A sample point 113 is also located on the discharge header of thetemporary hotwell pump 109 to allow the condensate to be sampled forboth particulate and none particulate contamination. Initially, thecondensate from the hotwell 20 will be highly contaminated with bothparticulate and none particulate contamination. The present inventionprovides for the installation of temporary waste condensate piping 114from the discharge of the temporary hotwell pump 109 to convey theinitial dirty condensate from the hotwell to waste. In prior artpractices, highly contaminated condensate from the initial steamintroduced to the condenser 18 and collected in the hotwell 20 cannot becompletely discharged from the system as this condensate is typicallythe only source of condensate to supply the suction of the plantcondensate pump 21. The suction strainer 23 on the plant condensate pump21 has only a limited capability to remove particulate contaminationfrom the hotwell condensate and is not capable of remove non-particulatecontamination from the hotwell condensate. Although prior art practicessometimes provide for the removal of a portion of the highlycontaminated condensate that is discharged from the system or cleansedby treatment through filters and possibly ion exchange resin beds,typically the majority of the highly contaminated condensate is returnedto the HRSG 3. As a result under the prior art, the time required tocleanse the system of fine particulate and non-particulate contaminationis significantly extended.

In the preferred embodiment of the present invention, as long as theanalysis of the condensate sample 113 shows the condensate to be highlycontaminated with non-particulate contamination, the condensate pumpedfrom the hotwell 20 will be discharged to waste 114. Once analysis ofthe condensate taken from sample point 113 shows the level ofnon-particulate contamination is sufficiently low to allow the return ofthe condensate to the HRSG 3, the discharge of the temporary hotwellpump will be diverted from the waste line 114 to a series of temporaryfilters 115. The temporary filters 115 are designed to remove fineparticulate contamination from the condensate removed from the hotwell20 by the temporary hotwell pump 109. The temporary filters 115 aredesigned to have the capacity to filter particulate contamination thatis as much as ten times smaller than the particulate contaminationremoved by the normal condensate pump suction strainer 23.

In the preferred embodiment of the present invention, the temporaryfilters 115 consist of a multiple number of filter vessels arranged towork in parallel to each other. The design of these temporary filtersallows individual filters to be isolated from operation and cleanedwithout interruption of the operation of the parallel units. In thismanner, high flows of particulate contaminated hotwell condensate can befiltered to remove large quantities of fine particulate contaminationfrom the condensate that would otherwise be recirculated back into thecondensate system 22.

From the outlet of the temporary filters, the condensate enters a cleancondensate header 116. A sample point 117 is located on the cleancondensate header 116 to provide a means of testing the condensate toinsure that it is sufficiently clean to be returned to the HRSG 3. Fromthe clean condensate header 116, temporary waste condensate piping 118is install to allow disposal of condensate that is not suitable forreturn to the HRSG 3. Once the analysis of the condensate sample takenfrom sample point 117 proves an acceptable level of condensatecleanliness, the clean condensate may be diverted through temporarypiping 119 to the suction of the plant condensate pump 21. A supply ofclean condensate to the suction of the plant condensate pump may also besupplied from a temporary clean condensate storage tank 121 throughtemporary piping 120. The reserve volume of clean condensate intemporary tank 121 provides an assured source of clean condensate to theplant condensate pump 21 until such time as the supply of cleancondensate returned from the hotwell 20 through the temporary filters115 is available. The volume of clean condensate in temporary storagetank 121 is also replenished by make-up demineralized water from theplant or from temporary water purification equipment supplied to thetemporary condensate storage tank 121 by temporary condensate supplypiping 122.

The temporary condensate storage tank 121 and the temporary condensatesupply piping 120 are sized to provide a sufficient reserve of cleancondensate to meet the condensate requirements of the HRSG 3 untilcleansed exhaust steam is admitted to the condenser 18 from the outletheader of the cyclonic separator 78 and clean condensate can be suppliedfrom the temporary hotwell pump 109 through the filters 115.

In the preferred embodiment of the present invention, a temporary cleancondensate pump 123 is also provided to transfer condensate from thetemporary condensate storage tank 121 to a temporary quench condensatedistribution header 124. The temporary quench condensate distributionheader 124 is designed to provide an assured flow of clean quenchcondensate to the various condensate injection points 38, 44 and 45 usedto control the temperature of the steam during the operation of the HRSG3 for the purposes of removing both particulate and non-particulatecontamination from the steam systems as well as to allow for thesimultaneous tuning of the combustion systems of the gas turbine 1. Dueto the potential harm that may be caused to various plant systems by asudden loss of condensate flow to the quench condensate injection points38, 44 and 45, one or more redundant temporary clean condensate pumps125 are also provided. In the preferred embodiment of the presentinvention, at least one of these redundant temporary clean condensatepumps is powered by a diesel engine or some other power supply separatefrom the normal plant power supply system. The volume of cleancondensate stored in the temporary clean condensate storage tank 121 andthe redundant temporary clean condensate pumps 125 provide assurancethat the system may be safely shut down in the event of a plant widepower failure or the mechanical failure of the primary clean condensatepump 123, the temporary hotwell pump 109 or the plant condensate pump21.

To provide further redundancy in the supply of clean condensate to thetemporary quench condensate header 124, the preferred embodiment of thepresent invention also provides for the connection of the temporarydemineralized water or condensate supply header 122 to the temporaryquench condensate header. In a preferred embodiment of the presentinvention, the temporary quench condensate distribution header 124 isalso supplied condensate from the discharge of the plant condensate pump21 through a temporary supply line 127

The significance of the ability of the present invention to remove highconcentrations of both fine particulate and non-particulatecontamination from the condensate that is supplied to the plantcondensate pump 21 as well as to the quench condensate injection points38, 44 and 45 is better appreciated when one considers the fact that theinjection of the condensate into the exhaust steam as well as theinjection of condensate, in the form of boiler feedwater, into steam inthe HRSG 3 will reintroduce any particulate and non-particulatecontamination remaining in the condensate back into the steam being usedto flush the system. The ability to more effectively remove bothparticulate and non-particulate contamination from the steam in a singleoperation provides for a cleaner system in less time and for theexpenditure of less fuel and high quality water.

In addition to the ability to simultaneously remove both particulate andnon-particulate contamination from the steam circuits of the HRSG 3 andplant steam piping systems 5, 9, 10, 11 and 16, the preferred embodimentof the present invention also provides for the addition of volatilechemical agents to the clean condensate by means of one or moretemporary chemical dosing pumps 128 that transfer chemical concentratesfrom temporary chemical storage tanks 129 into the temporary cleancondensate storage tank 121.

The temporary chemical dosing pumps 128 may be used to add agents toincrease the system pH to enhance silica removal as well as to addchemical agents to promote the formation of a stable passive film on theplant steam cycle metal surfaces.

Once the steam discharged from the high-pressure steam piping 5 isdetermined by the target insertion device 43 to be sufficiently clean tobe returned to the HRSO 3 by way of the steam turbine exhaust piping 9,the configuration of the steam path may be changed by the operation ofvalves on the permanent plant or the temporary piping systems. Incertain cases, the plant high-pressure steam bypass valve 30 may befirst opened to discharge steam from the high-pressure steam piping 5through piping 9 toward the exhaust of the high-pressure steam turbine,into the temporary piping 39 and through temporary valve 130 and finallyinto the steam exhaust header 43. Typically the maximum designtemperature of the plant piping 9 is lower than the normal operatingtemperature of the high-pressure steam header 5. As a result, it iscommon practice for the high-pressure steam bypass valve 30 to beequipped with a water injection system 131 to cool the steam that isdischarged into the high-pressure steam turbine exhaust piping 9. Thetemperature of the steam exiting the high-pressure steam section of theHRSG 3 may also be regulated by the operation of yet another waterinjection point 132 on the superheater section of the HRSG high-pressuresteam circuit.

When this above described practice is employed, it is done to removegross particulate contamination from the high-pressure steam turbineexhaust piping 9 before the steam is discharged back to the HRSGreheater 133. Once the exhaust steam cleanliness from the piping 9 asmeasured by the target insertion device 43 is deemed sufficiently cleanto safely direct steam flow through the reheater section 133 of the HRSG3, the configuration of the plant and temporary piping valves may bechanged to direct all of the exhaust steam through the reheater section133. These valve changes will include the closing of the temporary valve130 and the plant high-pressure steam bypass valve 30. In the resultingflow configuration the high-pressure exhaust steam is routed from thehigh-pressure steam piping 5 through the temporary piping 37 and 39 intothe exhaust piping 9 from the high-pressure steam turbine 6.

Once all of the steam is being exhausted through the reheater section133 of the HRSG 3, the temperature of the steam at the reheater exhaustmay be controlled by operation of yet another water injection point 134in the reheater section. The water used to control steam temperatures atthe injection points 131, 132 and 134 is typically obtained from theboiler feedwater pumps 135 that take suction from the low-pressure steamgenerator drum 136. The process and equipment described by the presentinvention assures that the condensate supplied from the condensate pumps21 through the condensate supply system 22 to the low-pressure steamgenerator drum 136 that is in turn supplied to the boiler feedwaterpumps 135 has been cleansed of particulate and non-particulatecontaminant concentrations that may otherwise impede the completeremoval of such contamination from the steam circuits being flushed bythe present invention.

The high concentrations of volatile chemical additives added to thecondensate supplied to the boiler feedwater pumps 135 by the temporarychemical injection pumps 128 provides a means of application of thevolatile chemical agents in the form of an annular mist directly to thesteam circuits being flushed through the aforementioned injection points131, 132 and 134.

Once the full steam flow is discharged through the reheater 133, thesteam flow will pass through the intermediate-pressure steam piping 11to the intermediate-pressure steam stop valve 13. Theintermediate-pressure steam stop valve 13 is kept closed or stoppled toprevent contaminated steam from entering the intermediate steam turbine12. From the hot intermediate-pressure steam piping 11, the contaminatedexhaust steam flow is conveyed by temporary piping 137 to the exhauststeam header 42. The contaminated exhaust steam that enters the exhauststeam header 42 is in turn cleansed by the combined treatment of thetemporary wash condensate injection points 44 and 45, the coalescersection 46 and the cyclonic separator section 58.

In the preferred embodiment of the present invention, the firing rate ofthe combustion turbine generator 1 is increased during the course of theflushing of the plant steam circuits to complete the initial tuning ofthe combustion systems. As the firing rate of the combustion turbinegenerator is increased, sufficient heat will pass through the exhaustduct 2 of the combustion gas turbine 1 to result in the generation ofsignificant volumes of steam from the intermediate-pressure steamgenerating section 138 of the HRSG 3. Typically the steam generated inthis section of the HRSG 3 is discharged into the inlet of the reheatersection 133 by permanent plant piping 10. Due to the higher firing ratesfacilitated by the capture of the exhaust steam condensate by thecondenser 18 as described by the present invention, the steam flow ratesgenerated from the intermediate-pressure steam generator section 133 aresufficient to provide a complete flushing of this section simultaneousto the flushing of the high-pressure steam piping 5, the intermediatesteam piping 9 and 11 as well as the reheater section 133.

As the firing rate of the combustion turbine generator is increased,sufficient heat will also pass through the exhaust duct 2 of thecombustion gas turbine 1 to result in the generation of significantvolumes of steam from the low-pressure steam generating section 139 ofthe HRSG 3. The steam generated by the low-pressure section 139 of theHRSG 3 is discharged through the low-pressure steam piping 16 to thelow-pressure steam turbine stop valve 17. This stop valve 17 is keptclosed or stoppled to prevent contaminated steam from entering thelow-pressure steam turbine 15. The contaminated exhaust steam isdiverted from the low-pressure steam piping 16 by temporary piping 140into the exhaust steam header 42.

The ability to effectively flush all steam circuits, high-pressure,intermediate-pressure and low-pressure simultaneously as described bythe methods and equipments of the present invention, further reduces theamount of time, fuel and high quality water required to remove bothparticulate and non-particulate contamination from the steam circuits.

The cleanliness of the exhaust steam is monitored by means of the targetinsertion points 29 and 43. The level of non-particulate contaminationis monitored by the sample points 75 and 113. The operation of the steamflush is continued until acceptable levels of both particulate andnon-particulate contamination are achieved and the initial tuning of thecombustion turbine generator combustion systems is complete. Experiencehas shown that with the high flow and temperature conditions generatedby the operation of the combustion gas turbine at firing rates well inexcess of those typically used in prior art methods, acceptable levelsof the cleanliness of the steam circuits can be achieved in as little asa single day of fired operation.

In the preferred embodiment of the present invention, once the mainsteam flow paths 5, 9, 10, 11 and 16 from the HRSG 3 to the steamturbine sections 6, 12 and 15 are acceptably clean, the plant valvesalignment is arranged to also steam flush the reheat bypass piping 84through the reheat bypass valve 33 to the steam distributor 34 in thecondenser 18. In the preferred embodiment of the present invention, theplant valve alignment on the low pressure steam header 16 is alsoaligned to steam flush the low pressure bypass piping 141 through thelow-pressure bypass valve 35 to the steam distributor device 36 to thecondenser 18. Although some prior art practices call for the mechanicalcleaning of these bypass lines prior to the initial flow of steamthrough these lines, the prior art does not provide any protection tothe thin walled condenser tubes 19 from any entrained contamination thatmay be flushed from these lines into the condenser. In the preferredembodiment of the present invention, a level of protection to these thinwalled condenser tubes 19 is provided by the installation of theimpingement shield 104 as previously described.

As applied to steam generation systems that combust coal or other solidfuels, the present invention will allow the steam circuits to be rid ofboth particulate and non-particulate contamination while the combustionburners, fuel handling systems, ash handling systems and combustion fluegas treatment equipment of the plant is initially tuned. The size of theparticular plant being flushed and the presence of multiple units mayresult in a requirement for the use of multiple temporary washcondensate injection systems, temporary coalescer sections, temporarycyclonic separators, temporary clean condensate storage tanks, temporaryhotwell pumps, temporary filters, temporary clean condensate storagetanks, temporary quench condensate pumps, and temporary chemicaladdition equipments. Variations in the configuration of plant pipingsystems will also result in variations in the configuration of thetemporary piping systems, target insertion points and sample pointsdescribed.

The foregoing disclosure and description of the invention isillustrative and explanatory thereof, and various changes in the methodsteps as well as in the details of the apparatus may be made within thescope of the appended claims without departing from the spirit of theinvention. It will now be apparent to those skilled in the art thatother embodiments, improvements, details, and uses can be madeconsistent with the letter and spirit of the foregoing disclosure andwithin the scope of this patent, which is limited only by the followingclaims, construed in accordance with the patent law, including thedoctrine of equivalents.

1-21. (canceled)
 22. An apparatus installed in a condenser and operativetherein, during the steam flushing of steam generation equipment andpiping, to enable shielding condenser tubes from direct impingement ofhigh velocity water droplets and particulate contamination entrained inthe exhaust flush steam that enters the condenser.
 23. The apparatus ofclaim 22 comprising woven wire cloth secured between the entry point ofthe steam into the condenser and the condenser tube surfaces.
 24. Theapparatus of claim 22 constructed and arranged so that there is uniformdistribution of the flush steam exhaust across the condenser tubesurfaces. 25-39. (canceled)